So, bottom line, right now I can't think of any other explanation other than the lack of actual gear, probably there is simply no mining gear available to keep the hashrate going up and at the same time some is not mining because it's either locked in warehouses that have stopped receiving cheap energy (the ones in Yunnan we discussed earlier) and they are to selling their gear or it hasn't reached the new customers.
One more thing to keep in mind is that many old gears are "stuck" in the "wrong" place, think of the guy who owns old gears such as 80w/th efficient and worse, that guy had to turn off his mining gears during the 2018 crash, that guy is located in Europe or in Newzealand where the power rate is 8-10 cents per kwh, selling his old gears means he has to ship them overseas, the price of shipping to where power is low enough to accept those gears is out of the question, so what does he do? turn them off and leave them be.
I would guess that there is at least 5-10EH of those guys, and they will eventually come back online as the price moves higher.
Another thing is dead gears that can be fixed for really cheap like the S9s, I personally have a lot of broken gears that I just don't want to fix now because it isn't worth it, but when and if bitcoin price is at say 50k I will take "fixing mining" as my primary daily job and fix every hash board I have.
The good news is those gears are small and thousands of them need to come online before they start affecting the difficulty badly, what worries me is the Jan-March 5nm gears that are going to be shipped, those gears are 100th on average, but until then, let's enjoy.
