He didn't use a car to commute before (I'd hope) given he was in the middle of SF. But now he likely needs one to get to the grocery, take his kids to school, etc even if he's WFH. And he's likely also using more energy at home, too. So yes, more pollution - and if a lot of other people moved there, higher prices too.

Well, if a neighbourhood is good and convenient, it is only natural that more people would like to move there, more energy would be consumed and prices would rise.

Besides this obvious thing, what exactly is your point?

The point is you haven't solved the problem. You've just moved it to a different place. Urban sprawl is pretty well acknowledged to be a bad thing (TM) - it increases pollution, is bad for people's health, bad for the social fabric, etc etc.

Saying "it's crowded here, let's go move somewhere else and make that crowded" is not just kicking the can, it's making the problem worse because often those areas have even less mass transit.