Blizzard is owned by MSFT now, so it did get bought out (back in 2022). So it fits the 'startup mode' model that I _think_ you're trying to say?
There's other studios that similar to Blizzard didn't get bought out early and published multiple hit games, like Insomniac Games.
Blizzard effectively got bought out when they merged with Activision. It wasn't technically a buyout, but Blizzard quality was never the same after that.
Blizzard has not been independent since 1994, but people on the internet love picking some arbitrary point in time when "Blizzard died" when in reality the timeline and quality of their releases has almost zero correlation with who they were owned by at the time.