Alternative take: overlords mostly meddle and oppress when it is profitable to do so, squeezing harder to get more sweet fungible tax-juice (or related monopolies).
They will also meddle and oppress unprofitably on occasion to make a display of power or as part of a scheme to siphon off money from elsewhere - but both these things are typical of expansionary phases, not contracting ones.
During contracting phases, overlords squeeze harder on the populations easiest to get to, even if they were previously the most loyal, and even if it destroys future revenues by doing so.