If you believe that crypto is a bubble, as I do, then the only way to profit off of it is by short selling.
There was no way to do this until the CBOT (?) opened futures trading a couple of weeks ago. Here's the thing about Bitcoin and short-selling. Short-selling is built in future demand. So, w/o short sellers, when the bubble crashes, it'll crash hard. No support at any level of short sellers cashing out by buying. Futures is a way to sell short in the future, but is it the same as naked short selling? Dunno. I've never worked in finance, so I can't say as to the mechanics.
But, market timing is very hard and as someone else posted "the markets can remain irrational longer than you can stay solvent." I believe that Bitcoin will keep going up until everyone that wants one has one. For me, I have all the Bitcoin I want (zero).