Yeah, the reasonable thing here is a stern talking-to about company policies, and then leveraging this thing to get more goodwill in the community about AI, which is an area Google is currently lacking in.

He probably got that talking to, and continued to be stubborn and unapologetic. Getting fired is quite difficult, as there will be multiple attempts at resolving any issue.

Google is sorely lacking in goodwill, period. I don't know why this guy got fired, and I don't expect we ever will know the whole truth. But even so this seems like a very foolish PR move for Google. Rightly or wrongly people are going to take his side, and they can't really afford to burn goodwill with their customers.