Lemmy is a federated system and these stats are self-reported by user maintained systems. Rather than a sudden influx of users (bots or otherwise), a misconfigured system or hiccup in stats collection seems more likely.
Generally, Hanlon's Razor, add applied to computing: Never attribute to malice that which is adequately explained by stupidityuser error.
There's a lot of malicious systems out there, but there is little corroborating evidence indicating that we're under attack.
Hanlon's Razor is all well and good as a heuristic, but tends to lead to people discounting malice much too often. Also, I really didn't say we were "under attack"
Look at the bottom with server count. Likely something screwed up there, and when those instances were suddenly returned, the user count was added back before being subtracted when they disappeared from the data.
Oh yes sorry. I invited my friends to check out the Fediverse. They tried it for a couple of days, but most of them ended up going back to Twitter and Instagram.