I realized this recently while playing a strategy game. There reaches a point where you’ve achieved the campaign goals, and there are no real threats to your power. So you figure hey, I’ve gone this far, I might as well work towards global domination. There’s no risk of not achieving world domination eventually, it’ll just be a grind. And the further you go, the easier and faster it gets. The alternative is quitting and starting a different game, and it kind of feels like a waste if you have to start again from scratch.
It’s like that with them. There’s no actual risk of loss, but gaining more is something to do. So they continue taking your previous success to its logical conclusion. There’s no quitting and starting again in this game though, since they’d still have all the money from their first success to fall back n. So there’s no escape condition, just a worthless grind to completion until they die. And everyone else suffers for it.