Why do they need to get filthy rich? Why not settle for rich and having a good game?

On a movie set, the director has a huge amount of authority. It's been baked into the culture for about a hundred years that the director is one step below God. A studio treats films as investments, but they also hire a director and (mostly) get out of the way. Sure, producers do meddle, but it's nowhere close to the same amount as with games -- and all the meddling is still pointed at the director, not the crew. I think this limits the damage that can be done.

Also, the film industry has strong unions. Most of the abuses in game dev simply aren't allowed. I suspect that the horrible culture of game dev can cause developers to stop caring, which bleeds through to the final product, and that won't happen to the same extent for movies.

"Popcorn movies" are a big thing, and most of those big investments are these. They're "turn off you brain for two hours and chill" events. A game, even the most chill ones, almost always last much longer and require more engagement. That is the defining trait of the medium. If you can totally turn your brain off then you didn't make a game, you made an expensive movie. Games, for players, are an investment. Movies often aren't.

Might be because you're not just spending 2-3 hours with games, but >30h, often hundreds or even thousands of hours. Making that a compelling experience that people don't quickly get tired of is much harder.

It's not. Plenty of game franchises are similarly profitable.