Which leaves the power grab theory weakened. It now has to be a failed power grab with an attempt to destroy the community as you flounce out.
Not impossible, but a pretty high bar that you'd expect would be accompanied by tales of how hard it is to work with these people.
Those tales are not being spread.
That leaves us back to the instigating incident model. But the mod team is taking confidentiality seriously, even as they resign. So we don't know what it is.