I think it depends in part on whether there are some good, short (!) tutorials on how to use Lemmy on Reddit.

People who just want to continue to browse content will be deterred from walls of text with technical details about the Fediverse and how Lemmy works. It should really be a step-by-step instruction… ideally offering a few instances to choose from at the start. So that the few biggest instances don’t break down from the influx and people leave again.

From my experience with unexperienced users, they will drop Lemmy like hot potatoes when they run into the first problem or broken down server.