LOL are you for real??? They had a stock pile because of the mining and they over produced thinking it was going to last longer than it did. The 1080 and 1080Ti sold in huge numbers. They sold so many 1070 and 1080 on release that they had a record breaking quarter.
People didn't buy Nvidia cards for mining. They wanted Vega cards because they were much better at it, when they were gone they moved on to 480/580s which is why you couldn't buy any for months.