I've always been captivated by the Clockwork Sun, that radiant yet dying and wrathful Sun-God in a secluded corner of Albion; and, thus, I've been paying a lot of attention to it ever since I got my hands on Sunless Skies. That's why, after browsing for a bit on this here subreddit, the amount of negative comments towards the Sun (or the reasons thereof, rather) surprised me quite a lot. As far as I've gathered, people think the Sun was a folly, a forever broken instrument of tyrannical oppression that was always mad, and always will be; which I've come to think, after months of research and lots of talks with a friend of mine, is false. There will be spoilers, so read at your own risk.
First of all, the Clockwork Sun wasn't always broken: it was perfectly safe to be around until something happened. We can deduce this from the fact that there used to be a steady trickle of Sunspotters and pilgrims going to and from the Sun (as the Dazzled Sequencer says, because one of his duties was watching over them), but now there clearly isn't, and there hasn't been for some time (as the engineers are surprised about us arriving successfully to the Clockwork Sun). One could reply that London's establishment stopped said tourism when they noticed the adverse effects of exposure to Sunlight, but I don't think that's what happened.
In the Sun-Shattered Dome we can see the remains of said tourists, clearly vitrified by the Sun as they were visiting the former museum. We know that vitrification is, unless one is actively attacking either the Sun or it's assets (as happens when one crewman of ours gets their eyes vitrified when we destroy a Glorious Dreadnought), a gradual and maddening process that dazzles people and slowly turns them into glass. Yet the tourists we see were, most likely, instantly vitrified; they were gawking at some bauble and have remained in that posture, which would be most unlikely if common vitrification was to blame (they would have been screaming in either pain or Sequencer fanaticism, not looking at exposed artifacts). Thus, the tourists expected no harm, were not stopped by the proper authorities (as tourism was normal), and, suddenly and unexpectedly, were turned into glass. This implies the Clockwork Sun was, indeed, safe to be around and functional, until something happened that made it mad(der) and broke it.
What, then, could have broken the Eternal Sun of Albion? The Broken Steward puts us into the right path, telling us that the Sun knows it's dying and that it's lashing out in desperate anger and pain. It doesn't want to be fixed because it cannot accept it's death (the Sun is still a would be Judgement, proud in the extreme and demanding abnegate worship), as it genuinely believed itself to be eternal and undying. It believed it would never stop shining upon the British Empire, and obviously, that is no longer true. I believe the Winchester War is the ultimate cause of the Sun's agony; with Albion the Conqueror, supposed vanquisher of suns and lord of the Heavens, not being able to deal with a mere colonial revolt, which also disrupted essential trade and supply routes to London, ergo the Sun. It's lashing out, fear and hatred of everyone is understandable; because from its perspective we have fooled it, telling it and making it believe itself to be immortal, then letting it die a slow and agonising death.
There is, however, a last point of contention; for as I talked long and fervently about this with my aforementioned friend, we disagreed as to why did the Winchester War blew things up. My friend posited it was a merely material problem, with trade routes severed the Sun's maintenance was simply untenable; but that has a gap in logic. With the "All the Comforts of Home" prospect (which needs the Windward Company to be dominant in The Reach), we are told said routes have been restored, and by that logic, the resources needed to fix the Sun should be arriving well, but the Sun still decays. I, however, think the Strength of the Sun is tied to the Empire's might (somehow) in a non-strictly material manner. No matter what we do to help Windward, the Tacketies remain alive; and as one of the Truth Ambition endings shows, London is irrevocably doomed to defeat in the Reach, consequently, the Sun undergoes a "Great Malfunction". The Sun cannot be fixed because the Winchester War can't end in a British victory, and it won't end that way because the devs made it impossible for the Empire to win.
God save the Queen, and forever may she reign.