This is a fantastic point. I watched several migration waves from Twitter to the Mastodon/*oma/*key network over the course of Nov-Feb and each became less impactful as instances and developers understood better how that traffic would flow. Consider also that those platforms had also been around for a few years already.
Lemmy and kbin are very, very young still, so it will be great to see them develop over the course of the coming months. I expect the next couple weeks leading to the June 30 3PA closures on Reddit will be spent preparing for another wave.