A cover up isn't very hard to execute if the involved parties all have aligned incentives - in this case, not ruining their careers, possibly destroying their entire professional field, and publicly accepting culpability for millions of deaths and other damages.
In a leak? Zero would be the minimum who would have knowledge of the leak. There is no law of the universe saying that anyone would be aware of what had happened or how, especially with an active disinterest and disincentives toward responsibility and accountability.
Not that many, probably 1, or maybe 3 to be conservative. Of course there are the institutional and governmental parties as well, but still not that many (1 lab director, maybe 1 executive above them, plus a handful of regulators with detailed knowledge of the labs operations). If it is the case that, say, the WIV leaked the initial virus, there's probably less than a dozen people in the world with positive knowledge of that fact.
I've seen fundings and positions related to COVID research popping up since at least mid 2020. Biorxiv submissions exploded. Certainly not a small group to deal with.
