The stock market isn't poised to crash anytime soon (except for the flash crash that will occur when Wall Street figures out they're not safe from Trump's destructive flagellations), and while crypto will be a rougher ride, it's still in a general upward trend as it comes into its potential.
However, most cryptocurrencies are like precious metals in that they're inherently more crash-prone than fiat currency. With fiat currency, there are monetary authorities that can take policy actions to stabilize price fluctuations and prevent inflationary and deflationary spirals.
With something like gold or bitcoin, there is very little (transaction fees, mining effort, but look how little they seem to matter to price!) to arrest the self-reinforcing ascent, where everybody buys and holds, since the price is rising, and since few are selling, the price continues to rise.
But there is also very little to soften the inevitable self-reinforcing descent, where everybody sells, and since few are buying, the price continues to drop, causing more people sell in order to keep from going bust.
If you're afraid of a crash of some kind, invest in assets, not currency, that will keep their value in such cases.