There are a shit load of GPUs mining ETH and other coins out there. The moment this became as profitable as ETH for RX580s and similar, it begun drawing them. Instead of Monero mining going insanely profitable as some expected, I think all GPU mining will be a speck more profitable, and that's it.
plus I think from this we now know a large portion of the eth hashrates are probably asics as well which cant switch to v7 so i think eth hash rate will only drop say 15 perect mac