Bella Maria, I agree with you totally on why michael decided to get into Immobilaire. He also wanted it to provide a good income for his children when he's gone that was legitimate, so that their heritage as Corleones will no longer be tarnished.

As for why the Archbishop worked for Luchisi, that's a good question. Maybe he didn't want to work for Luchisi becuase Luchisi wouldn't help the Vatican out of the financial troubles it was having. Luchisi was an evil and dangerous man. Perhaps the Archbishop saw Michael as less threatening to himself, but a good adversary for Luchisi.