My assumption: There were a number of rigs that got powered down by around mid-May as they no longer remained profitable when the exchange rate collapsed. When it was apparent the price wasn't going to quickly rebound (i.e., in a bear market) there were then decommissioned, boxed, and sold to someone else who has a lower cost of electricity and are now being powered back on.

Similar sentiment stated in the mining section of this weekly newsletter:

Blockware Intelligence Newsletter: Week 53 #65782 https://newsletter.blockwareintelligence.com/p/blockware-intelligence-newsletter-fba