As Matt Levine would say, the way to do that is to mint and sell your own NFT. That way you are on the opposite side of the trade as the bulls who you believe are wrong.
If you mint an NFT and fail to sell it, you'll lose the minting fee. You'd do better to hold off on minting it until it has already been sold. And to actually sell some, you need to market them as something that people would want (like "saving lives") or, if you're short on ideas, crowdsource that task. At which point you're basically running an NFT platform. And you'll make more money the longer the NFT craze runs, which isn't really opposite to the bulls...
The proper way to bet on NFTs being passé soon is probably to invest in something that's not an NFT.