It’s run through the Open Collective, and is also run by Ruud who runs one of the larger Mastodon instances as well as some other stuff on the Fediverse I believe. They’re a fairly trusted actor in the space and I think pretty transparent with everything they do which is probably another reason many people flocked there.
My first thought was AstroTurf too but honestly Lemmy is still small enough that I wonder if Meta even cares enough for it to pay for astroturfing here. They got more signups in a couple of hours than Lemmy got users in three years, and by several magnitudes even. Plus it’s an inherently hostile demographic for them. They’re better off investing in positive posting on Reddit, which I’m sure is what they’re already doing.