This sounds really dumb, but the "activity" is primarily what draws new users and keeps existing ones. The primary complaint/desire of new Lemmy users is more/sustained activity on the platform. That's also what keeps people using Twitter and other SM platforms.

For a company approaching an IPO, increasing amd sustaining activity from real users is maybe the second most important thing to do, second only to showing a clear route to monetization. It doesnt surprise me their team may be mostly admin and "community builders", but it does surprise me that they'd risk loosing major contributors and moderators without a clear replacement.