There is more info about the hash rate spike on the monero reddit posted at
https://www.reddit.com/r/Monero/comments/agysnf/hashrate_discussion_thread/Basically to sum it up the hashrate is not coming from the 3GB GPUs which can't mine ETH anymore since the ETH difficulty hasn't changed enough to account for the increase. Plus they are also not profitable.
Some FGPA manufacteur claims that its possible to make a 100kh/s FGPA. And most likely they are trying to ROI as fast as possible before an ASIC or another faster FGPA is released before the algo forks again. Seems it only takes about 2-3 months or so to develop an FGPA.