Doing some research I've found that is estiamted that 3 million gpu's were sold to miners just in 2017, according to this information:

https://wccftech.com/amd-nvidia-intel-q4-2017-gpu-market-share/

and this just in 2017, in addition nvidia miners in the past has other algos that it was more efficient than eth, but in 2018 most of the time eth were the more profitable algo (I'm speakin about most known algos).

So maybe all the hashpower entering the eth network is not just asics.