It's the bitcoin mining craze. There are now many very large "mining farms" with hundreds of GPUs each. We have several in the Québec province of Canada because we have the lowest electricity prices in North America. Mining is very energy intensive and is not profitable for individuals on a single computer.
Unless the GPU manufacturers find a way to increase production dramatically, we will be stuck with this problem until the bitcoin bubble bursts--which it will, sooner or later. In the meantime, search regularly and often and where possible sign up for a notify me when in stock alert.
"Bitcoin hit a high of just under $20,000 in mid-December 2017 after increasing about 20x since the beginning of 2017. It then went on a fairly steady decline to a low around $6,000 on February 6 (...).
"(...) Starting on Wednesday it started to climb above $9,000 and on Friday crossed $10,000. Arguments can be made that Bitcoin could fall to $1,000 or rise to $100,000, but at least for now Bitcoin appears to have steadied itself."
--Forbes
https://www.forbes.com/sites/chuckjones/2018/02/17/bitcoin-may-have-found-a-bottom/#28dfa4768f96)
Also, the US government announced recently that cryptocurreny regulations will be coming "soon".