It's not like he can't hire a maid or a decorator to do that work for him if he doesn't have the mental bandwidth and is making such good money though.

You're right, it's not his place. And you're right, he should be able to prioritize/reprioritize as he needs. Right again that your mom overstepped here.

But at some point you're choosing to to a slob and that's often indicative of something going on internally. Maybe mom should collect some business cards of maids and decorators if it means so much to her or just accept him as he is.