it's easy to make many, and pretend that they are legit.
The other aspects of an NFT, such as it being created by a trusted authority (like the original artist) is not encoded on the NFT itself. You have to trust the minter, you have to trust that other people see the minter as original, and you don't truly have a way to verify except via an existing social structure. aka, technology cannot solve this problem.
That is why i call NFT a digital certificate of authenticity. It has the exact same problems as the paper version of a certificate (obviously, a digital version has some good utility like ease of trade/uncopiable and verification etc).
If they won't even do that much, what's the point?!
The answer is that the NFT represents the artwork, not the bytes in any particular file, in the same way that intellectual property law recognizes that the painting on your wall is merely a particular instantiation of the real, immaterial artwork that is protected.
The trick is to understand that neither links nor hashes are a key component of the concept (though both are useful to create a link between ownership record and some kind of representation of an artwork).
NFTs don't really solve many problems.