Twitter's daily active user count has gone up since Musk took over. If people were chased off, they either came back or others filled up the numbers.
Anecdotally, I've enjoyed Twitter a lot more since his takeover. They've relaxed their rules and unbanned a lot of people who I'd missed seeing on the platform. Musk does seem to be at least partially keeping his promise of improving the free speech aspect of the site.
That ten million figure includes the many of us who created an account on some instance, had a browse around for a few minutes, realised it was a boring wasteland of a service, and never logged on again.
Let's see the data for active users, not just registrations.