Are the same Dev's who make the game responsible for the updates?

I was just wondering if it is the same dev team who makes the games, as the team who update the game after release.

To me it seems the game if usually alright on release and then made subsequently worse and worse with the updates thereafter. I was wondering if it is the same team working on it? It just seems really odd because I can't understand why they would undo all their work... and proceeds to essentially slowly change the game to FIFA 22 after they release it.