So, how can we tell?
The best evidence we have is this statement from the mod team:
"We recommend that the broader Rust community and the future Mod Team exercise extreme skepticism of any statements by the Core Team (or members thereof) claiming to illuminate the situation."
This is a nasty example of poisoning the well.
<We won't say what happened, but don't believe them if they do.> Gross.
This nasty well poisoning makes me lean toward the power grab model. But that doesn't make sense, because the mods resigned; they can't take power.