There was lot of people recommending BlueSky over Fediverse, when the big hype happened. The biggest problem to me is, that this split up the user base considerably. Which in turn weakened its potential for both platforms to overtake Twitter.
Just under us: If you want so, we took Twitter over. It’s renamed to X. :-p …, nah, just joking, it’s still Twitter.
I don’t know where you got that number from, but at least these statistics say Mastodon got 9 million users (but not all are active off course, same should be true for BlueSky): mastodon-analytics.com And this account claims 15 million: mastodon.social/ and a Wikipedia article says “On 19 March 2023, Mastodon passed the ten million mark for registered user accounts”: en.wikipedia.org/wiki/Mastodon_(social_network)#2…
Now, I do not claim these numbers to be correct. But compared to your estimation its vastly different.
At least Bluesky is decentralized and Open Source, isn’t it? While this is a conceptual step down from Fediverse, it’s still better than all the other alternatives in use. I don’t know how much the Bluesky company controls the entire platform, if its even possible.