[Media: https://bsky.app/profile/bsky.app/post/3l47prg3wgy23]
After attracting 2 million users in its first year of operation, Bluesky has grown another 400 percent with some recent help from Brazil and Elon Musk. Are these monthly or daily users, or just account holders? Nobody knows! But it still has a way to go to match X’s estimated 250 million daily users and Threads’ 175 million monthly users.
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.