Except that's next to impossible to short BTC without incurring major exposure to the crypto market as a whole in process. In other words, you can gamble that BTC will go down all you like in the wonderful world of DeFi, but if your gainzzz are in $random_shitcoin then the fiat value of that will also go down the toilet.

The closest you can do is shorting BTC-adjacent regular stocks like MSTR, MARA, etc.