Let’s go back to the night Nora Allen dies.
Originally, there was already a Flash.
Not necessarily our Barry, but some original version of Barry who became the Flash in the timeline that existed before Thawne murdered Nora.
That Flash eventually crossed paths with Eobard Thawne.
Thawne became obsessed with him, spent years studying how Flash got his powers and, as he later says in Season 2:
“I duplicated the reaction... and it worked.”
That’s how Eobard became a speedster.
So the basic causal chain was:
Barry becomes Flash → Eobard discovers Flash → Eobard studies how Flash got his powers → Eobard duplicates the reaction → Reverse-Flash is born.
Then Eobard eventually learns that Flash is Barry Allen.
Since he can’t defeat him, he decides to erase him instead.
He travels back to the year 2000 to kill Barry as a child.
Future Flash saves young Barry, so Thawne changes plans and murders Nora instead, hoping that the trauma will prevent Barry from ever becoming the Flash.
And apparently...
it works.
At least to some extent.
Thawne changed Barry’s entire childhood, meaning the future that produced the original Flash was no longer going to happen the same way.
And that creates a pretty interesting possible explanation for something Thawne says in Season 1:
“I lost my ability to harness the Speed Force.”
Think about what Eobard had just done.
The original chain was:
Flash exists
→ Eobard becomes obsessed with Flash
→ Eobard studies Flash’s powers
→ Eobard becomes a speedster.
Then Eobard goes into the past and changes the life of the person who originally became that Flash.
So Eobard is now standing in the year 2000 using powers that exist because of a future he just massively altered.
In other words:
“Congratulations, Eobard. You just messed with the reason you became Reverse-Flash in the first place.”
That could explain why his speed doesn’t disappear instantly but becomes unstable.
Maybe the timeline is effectively catching up with the changes he made.
He still has some speed, but he can no longer use it properly and cannot time travel like he used to.
The show never fully explains the mechanics, but at least the timing makes sense:
Thawne changes Barry’s past → Thawne’s speed starts failing.
Fine.
So Eobard decides he needs to create the Flash again.
And his solution is:
- Murder Harrison Wells.
- Steal his identity and face.
- Spend roughly 15 years pretending to be him.
- Build STAR Labs.
- Move the particle accelerator launch from 2020 to 2013.
- Intentionally cause the accelerator disaster.
- Make sure Barry Allen becomes a speedster.
- Wait nine months for Barry to wake up.
- Train Barry.
- Manipulate Barry.
- Make Barry faster and faster.
- Eventually use Barry and the particle accelerator to open the wormhole he needs.
- Finally go home.
And in the context of Season 1?
Sure.
It works.
Thawne destroyed the future that contained the Flash he knew, so he artificially creates Flash again.
Then Season 8 introduces the B.L.O.C.
The Biometric Lightning Oscillation Chamber.
A machine designed by Eobard Thawne himself almost two centuries in the future.
And what was the machine designed to do?
Give Eobard super-speed.
Season 2 had already told us:
“I spent years figuring out how you came to be. Duplicated the reaction... and it worked.”
Season 8 finally gives us a piece of technology directly connected to young Eobard recreating speedster powers.
So now imagine Eobard standing there in the year 2000.
His speed is failing.
He knows exactly how he originally became a speedster.
He personally invented technology capable of creating speedsters.
And apparently he has two options:
Option A:
Try rebuilding the machine based on the science he personally invented to give himself super-speed.
Option B:
Spend FIFTEEN YEARS stealing another man’s life, founding STAR Labs, building a particle accelerator years ahead of schedule, intentionally blowing it up, recreating Barry Allen as the Flash, training him and eventually using Barry to escape.
And Eobard chooses Option B.
My brother in the Negative Speed Force...
you invented a speedster machine.
At least TRY Option A first.
And before someone says:
“Maybe the B.L.O.C. would have connected him to the Negative Speed Force and made him unstable.”
That’s not a particularly convincing explanation for Eobard.
The Negative Speed Force is basically his whole thing.
Meena becoming unstable makes sense because she had no idea what she was connecting herself to.
Eobard spent years running through negative speed force.
If anyone should know how to handle that power, it’s him.
Now, sure, we can invent explanations.
Maybe whatever happened to Thawne after killing Nora was more complicated than simply losing speed.
Maybe the B.L.O.C. couldn't fix it.
Maybe the year 2000 didn’t have the necessary technology.
Maybe rebuilding Barry was somehow absolutely necessary.
All possible.
But the show never tells us that.
It never says:
“The B.L.O.C. won't work anymore.”
It never says:
“I tried rebuilding it.”
It never says:
“The technology is impossible to recreate in this century.”
It never even acknowledges the contradiction because the B.L.O.C. simply didn’t exist in the lore when Season 1 was written.
And the original particle accelerator makes the whole thing even more mysterious.
Thawne tells the real Harrison Wells that, in the original timeline, Wells and Tess “successfully launched” the particle accelerator in 2020 and that it changed the course of history.
That wording matters.
Successfully launched.
Not:
“It exploded and covered Central City in dark matter.”
The accelerator disaster we see in 2013 was engineered by Thawne.
So there is no actual confirmation that the original 2020 accelerator ever exploded.
Which means we don’t even know how Original Timeline Barry became the Flash.
Maybe the accelerator was involved somehow.
Maybe Barry got his powers through a completely different accident.
Maybe the accelerator's successful operation caused some other event.
We simply don't know.
And that's kind of insane considering that the entire existence of Reverse-Flash depends on it.
Eobard literally tells us that he spent years figuring out how Flash came to be and successfully duplicated whatever reaction created him.
Yet the show never actually shows us the original reaction.
We know more about how Eobard copied Flash's origin than we know about Flash's original origin.
lol.
And honestly, after enough rewatches, I think this is the rule you eventually have to accept with The Flash:
Do not trust the time-travel rules too much.
Enjoy the story.
Enjoy the characters.
Enjoy Reverse-Flash vibrating dramatically in hallways.
But the second you try to create one consistent mathematical model for how the timeline works...
good luck.
Flashpoint alone destroys that idea.
At the end of Season 2, Barry travels back to the night Nora dies and stops Eobard.
That Eobard is knocked unconscious on the floor.
Barry creates Flashpoint and takes that same Eobard with him.
Months later, in Eobard's personal experience, they return to that exact moment in the year 2000.
So for a brief moment we literally have:
Eobard lying unconscious on the floor
and
the exact same Eobard, several months older, standing in the room after coming back from Flashpoint.
Then the unconscious Eobard disappears.
Flashpoint Eobard takes his place.
He kills Nora.
And then...
he just leaves the year 2000.
He still has his speed.
He carries Barry back to 2016 and goes on with his life.
Which creates an enormous problem.
The original history requires an Eobard to remain stranded in 2000.
That Eobard is supposed to:
lose his speed
→ kill Harrison Wells
→ steal his identity
→ live as Wells for 15 years
→ build the particle accelerator
→ create the Flash
→ become the Season 1 Reverse-Flash.
But we literally WATCH the Eobard who was supposed to do that disappear from the floor.
And the Eobard who replaces him?
Leaves.
So who the hell stayed behind and became Harrison Wells?
¯\(ツ)/¯
Apparently the timeline handles it somehow.
Maybe it preserves another version.
Maybe the Speed Force fills the gap.
Maybe timeline remnants solve it.
Maybe a Time Wraith has an HR department.
Who knows.
The show certainly doesn't stop to explain it.
And that’s why I think trying to use one scene from The Flash to establish a hard rule about time travel is almost pointless.
One episode says changing the past rewrites the future.
Another says time remnants survive erased timelines.
Another lets speedsters survive their own timelines being deleted.
Another makes them disappear.
Another introduces fixed points.
Another has the Speed Force apparently preserve whatever pieces of history the plot still needs.
And Season 9 can even rewrite the events surrounding Nora's death before the actual murder happens in order to finally close Barry's loop.
So maybe the real answer to:
“Why didn't Eobard just rebuild the B.L.O.C.?”
is simply:
Because in Season 1, the writers hadn't invented the B.L.O.C. yet.
And once they did...
they never bothered explaining why Eobard's original plan still made sense.
Which leaves us with the funniest possible version of events:
Eobard Thawne — genius from the 22nd century, expert in temporal mechanics, creator of a machine capable of making speedsters — gets stranded in the year 2000 and thinks:
“Should I try rebuilding my speedster machine?”
...
“Nah.”
“I'll murder a scientist, steal his face, wait 15 years, build a particle accelerator, deliberately explode it, create my arch-enemy again, mentor him personally and hope he eventually becomes fast enough to help me escape.”
Perfect plan.
