What could possibly explain this highly periodic crash in overall network hashing speed? I think this is not a random thing, but rather some effect due to actions taken by minors. What is going on? That is a pretty strong down trend late in the cycle.
Livenet testing/shipping cycles could help explain some of it.
Test Lot 1 causes the first increase. Shutdown Lot 1 and ship causing the first decrease. During the second cycle, Test Lot 2 while at the same time Lot 1 is arriving at the purchasers and being powered on. Test Lot 2 gets shut down and shipped to end users. Test Lot 3 comes online for testing while Test Lot 2 arrives at the end-user.
Rinse. Repeat.
However, I think this scenario, while possible, is unlikely as a manufacturer wouldn't necessarily start/test/shutdown/ship in lots like this. They'd probably cycle HW in and out of deployment testing and shipping.
some entity switches on their quantum computer prototype in the middle of the cycle, then powers it off as not to cause too much disturbance.
It helps with the expenses,
.