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): https://mastodon-analytics.com/ And this account claims 15 million: https://mastodon.social/@mastodonusercount and a Wikipedia article says “On 19 March 2023, Mastodon passed the ten million mark for registered user accounts”: https://en.wikipedia.org/wiki/Mastodon_(social_network)#2022_Twitter-related_spikes_in_adoption
Now, I do not claim these numbers to be correct. But compared to your estimation its vastly different.
Edit: Just for context of my reply, as you edited yours. You said you don’t believe Mastodon would even have 100 thousand users.
Even if your numbers are true. Mastodon has existed for 7 years. Bluesky for less than one.
So logically the precentage of users to active users should be much higher on Bluesky.
Also number of accounts is possibly a bad metric to judge mastodon because of the federation.
For example, I have 8 mastodon accounts (tried a couple different instances and programmed a couple rss bots to give me a news feed).
Even if your numbers are true. Mastodon has existed for 7 years. Bluesky for less than one.
That doesn’t matter, because most users just came in the last year. Just shortly after Mastodon begun to explode in 2023 from 2 million to over 10 (and now seemingly over 15 million) registrations, Bluesky came in. So the 7 years comparison doesn’t matter here.
So logically the precentage of users to active users should be much higher on Bluesky.
Probably, but without statistics its just our gut feeling. And as you saw a few minutes ago, your gut feeling can be drastically wrong. My point was not here to race count Mastodon vs Bluesky, but to point your estimation of Mastodon accounts being vastly underestimated.
According to Wikipedia Bluesky has 10 million users and 5 million monthly active: https://en.wikipedia.org/wiki/Bluesky That would be about what Mastodon has, if we believe those numbers. My point is, you totally over estimate Bluesky and underestimate Mastodon. The exact numbers does not matter here, what matters is my point that the user base is split into these two worlds.
So bluesky has 5 million monthly active users while mastodon has 1 million?
Thats a fivefold difference.