There’s certain common patterns this dynamic seems to take:

• They end up in that type of traditional marriage for fifty years where the wife controls absolutely everything and the man throws around jokes about ball and chain. This ends when either one dies; if the man dies first, the wife will live happily for another ten years, but if the wife dies first, the man follows soon
• The man loses all sights of himself and becomes a passive and meek “yes, dear” -man, and then the girlfriend (or wife if they managed to get married) eventually gets bored since the project car isn’t fun anymore, and cheats or just straight up leaves him. This pattern might also involve straight up domestic violence where the man is too embarrassed and scared to seek help
• The girlfriend (or wife again) gets tired of taking care of a manchild instead of having an equal partner, and leaves. This happens especially if they have children and the wife realizes it’s actually easier to take care of the children alone. Often the man also ends up whining about how he doesn’t understand what he did wrong, and thought everything was going so well