I mean, I heard they hired Ninja. And Dei tried to do Jackbox night on Mixer one time before we found Discord was just better... and I know the PA guys did their streams there a few times... but that was about it.
You're not going to dislodge Twitch - and by Twitch, I mean *Amazon*, without considerable willingness to just hemorrhage expenditure until you've cracked their marketshare, sort of like how Epic is doing with Steam. They took all their fortnite money and poured it down the drain (by which I mean gave guarantees of revenue to every developer they could sink their talons into in exchange for timed exclusives), and I begrudgingly admit they've made headway.
But Amazon is several orders of magnitude bigger than Valve. It'd be like trying to make your own Youtube, with blackjack and hookers! Speaking of, really, I'm impressed that Vimeo is still in the game. But they've never been a serious contender or threat to Google's stranglehold on the user-made-content-hosting market - again, the closest competition is Twitch, which isn't even really in the same vertical.
I guess microsoft decided they weren't ready to throw away THAT much money, much like when Google dabbled briefly in, and then ran away screaming from, the broadcast radio industry.