The cynic in me believes this is motivated by not Musk's love for the "mission", but by xAI, his attempt to build OpenAI's competitor. I'm guessing this is just a way to weaken a competitor.
I feel like we now have a reasonable expectation that his AI effort becomes open source. Not that I actually expect it, but seems reasonable in this context.
Now that this accidentally created something even more powerful (and Tesla's autopilot plans don't seem to be panning out), he's trying to stifle the competition so that xAI can catch up. SPOILER: They won't.
This requires less cynicism than seeing through that Putin invaded to denazify Ukraine, or that your corporate employer rewarded you with pizza because they care about you.