TL;DR: The current Mastodon-signup is only removing the confusion of users on first glance, because it either hides the server-choice altogether, or leaves them with a choice that is impossible to make at this point of their Mastodon-journey. Instead, it should introduce them to decentrality on a lower scale, with a handful of handpicked servers to choose from, such that the decision makes sense to them and shows them the merits and fun of the concept instead of scaring them away. Ideal would be to give them a sense of agency. Then, chances are higher that they consider migrating again in the future and eventually internalize it as a permanent option of the digital world.
I just did this the other week, all of your followers (who are on servers that are still online of course) will follow your new account and unfollow the old account.
It was a bit funny, because I had already signed into the mobile I used and was flooded with notifications as each account followed me (some might be slightly delayed, but all in all it didn’t take more than an hour for the ~50 followers I had).
You will however want to export the list of people you follow from the old account though, because that isn’t automatic. Once you plug the export file into the new account though it’ll do the rest for you.
That sounds very slick. I never really used twitter so had no reason to use mastodon instead, but I am glad it exists!