LA has all the existing infrastructure to host the games. Several probably need adapting and modernising but it's largely ready to go. Paris, like London, did a great job of turning historic sites into venues for the Olympics and didn't need to do a new stadium the way we did either. But whilst there has been a huge amount of credit for the games, I stand by the fact that swimming in the Seine was ridiculous and the sailing events were a disaster. Not too much have been made of either, but when you're looking to host a number of sporting events you would imagine picking a place with wind or an outdoor swimming venue that isn't polluted to fuck should be quite high on the agenda.
LA will do exactly what it already has, roll out the stars and sell things that way.