It has to decline, I was giving it 2-5 yeas, but it seems it dropped much faster: https://news.ycombinator.com/item?id=15760415
As for the faster than usual now, my guess is few things. Main contribution is NVidia that had their earnings report, they told the planet flat out gpus aren't selling as well, so the gig that everybody is increasingly mining was called up. Normal people check out, traders can't trade if they can't short it and it's starts going downhill. So anybody that's in the business of not losing money stops the bots. But nvidia the most visible thing that creates sentiment among the crypto-evangelist population it seems.
The other reasons wound be, end of a 40 year bull run across western democracies, end of the minor cycle economy run, add to that a trade war, QT, people overexposed on the houses with HELOCs and stuff from that QT, and everybody will be pulling cash from everywhere since cash will matter fairly soon.
The rest is standard, stock market drop by 20% or much more, asset bubble deflation, etc etc. It's all fairly cyclical.