what happened is vast majority of miners just got up and left as soon as diff increased
Absolutely untrue. Hashrate was for weeks around 0.5. Recently it peaked at 3.3 and now it's at 1.76. At no point "vast majority of miners left", stop lying.
look here
https://cash.coin.dance/blocksin the last 12hrs only unknown, viabtc and 2blocks by btc.com
before there were btc.top, f2p, ant, bat, uu where are they now?
Bitcoin cash difficulties raise so they all gone to mine bitcoin. You will see this kind of activities after every 2 weeks when activities increase and decrease according to hash power.