Zcash difficulty took a pretty big drop today. No clue why but Im going to enjoy it while its here.
There are other equihash coins - might have been a shift to one of those.
Could also be some GPU miners pulling rigs due to low profitability, or shifting to other more profitable coins.
Could also be normal "luck" variation.
I suspect it's a combination of "all of the above" though.
Agree with your points. As a conspiracy theory junkie its more fun to think bitmain is shutting down their units after testing , in order for them to be packaged and shipped.