I don't necessarily believe all crypto is going to zero, but for Bitcoin specifically I believe (a) that proof of work is definitely unsustainable as the market cap grows and (b) given the power of miners in the BTC protocol, I have a difficult time believing they'll ever transition off PoW (e.g. compared to what ETH has done).
But, of course, shorting an asset requires conviction not just that its value is going down, but when. I would easily bet that within some decent extended time period, say 15 years, that the value of BTC will be zero or near zero. I am unaware how to short an asset feasibly over that long of a time period.
I don't use Reddit or any other social networks. This is the only site I post anything on. My suggestion to put a trade on instead of just saying stupid things on the Internet comes from institutional trading culture.
Anyone can say anything. Almost nobody backs it up with money.
It's questionable that Bitcoin has any value but there is enough money sunk into that ecosystem and propping it up that it's unlikely to ever fall away completely. There are billionaires' egos at stake here!
The market can stay irrational longer than you can stay solvent. Shorting for any decent stretch of time is not free, and you more or less have to do it on one of the many rigged casinos operating in the crypto space. It's a fool's game.
If you want proof, refer to what happened in the lead-up to the 2008 Sub-Prime Mortgage crisis (or check out the movie The Big Short if you want somewhere to begin).