Right, but that's where absolute and relative come into play.
200k new users per week is... what, 0.05% - 0.1% of Twitter active user base?
Not saying one day it might not snowball, but it's been 6 months and I wouldn't call Mastodon an existential threat to Twitter just yet. I am tremendously enjoying and schadenfreuding the twitter melodrama, but even most people making fun of twitter/musk/socialnetworks, seem to be doing it on twitter.
My mastodon timeline has been growing pretty rapidly over the last year. With obvious ratcheting up happening whenever elon steps on yet another rake. 'Let that sink in' nearly doubled the amount of posts per day, 'hardcore mode' another, 'api shutdown' another...
Anyway, I think it's more relevant that many accounts are now also syndicating to Mastodon, which makes it a viable alternative for consuming users.
It's far from being an exodus, but they are averaging 200k new users per week, which seems pretty good.