I mean, isn't this exactly what we would expect? Big influx of people when reddit does something unpopular and people want alternatives, then a decrease as the anger fades and people either decide they don't like Lemmy for some reason, or just settle down into their normal, less active amount of posting, stabilizing at a number of users lower than the peak but higher than before the influx. Assuming that Lemmy still is around the next time Reddit gets people mad, it'll happen again, just like how Mastodon gets an influx of new users whenever Twitter does something to upset it's userbase.