Why did Meta release theirs? The better question is, why not? If you aren't at the cutting edge and don't have a moat then releasing them is pure reputational upside with zero downside.
You might even get lucky and someone else does the same. If you manage to learn from their example you might be more competitive in a future round.
I think we are now in the era of oligarchies, and oligarchies maintain power by being highwaymen and extracting tolls, in a kind of rentier capitalist structure.
By throwing LLM models out into the commons, China is disrupting the possibility of this taking hold there.
God bless 'em