@edma That's a rather idealistic view that only seems good for you because you aren't in her situation. Being an idealist won't make you a good ruler, since you'll have to make decisions that will go against it, rather often. None of the so called ideal rulers throughout in history were that much of a good guys, if you look at them partially they all did some shady shit. Anyone that was truly an idealist got the short end of the stick. By the way the basic human instinct is survival, hence why she did everything she could to avoid her death in the first place. Keeping him beside her, however "noble" he is, which is also sort of a joke imho, is contradicting that instinct, and the logic that the premise of the series was built upon. Especially when you say "it's a good thing". Therefore the story falls apart whenever Eusto is involved something, even only as a side character, not to mention when he gets an important role.
As for his wouldn't overthrow thing. The motherfucker were unable to realize that she was drugged for years by the prime minister, hence the way she turned out, so assuming that he'd do anything remotely smart is thrown out of the window from that point. That stupidity is what keeping him close makes it so dangerous, because he doesn't really think or plans before he does something. That's why his fate in the original route was rather karmic and well deserved. By the way, if we dig deep down onto his character, it all comes to the fact that he wasn't able to take the fact that she fucked anyone but him, hence it was just easier to get rid of her.
@doctorstrangelove Democracy itself is a system that bleeds from a thousand cuts. Aside from what skillodracus said, it's rather egoistic to think that it would serve the best interest of everyone to implement it.