It seems though that Linus didn't make this decision for political reasons, but instead because he doesn't want to get in trouble with the US government. He indicated that he was advised by lawyers to do this:
I'm not going to go into the details that I - and other maintainers - were told by lawyers.
He probably isn't too bothered by the sanctions given his comments about his Finnish nationality being a reason why he opposes Russian aggression. But still, it seems at the moment he's just trying to follow the law.