Ethereum makes it possible for NFTs to work for a number of reasons:

Transaction history and token metadata is publicly verifiable – it's simple to prove ownership history.

Once a transaction is confirmed, it's nearly impossible to manipulate that data to "steal" ownership.

Trading NFTs can happen peer-to-peer without needing platforms that can take large cuts as compensation.

All Ethereum products share the same "backend". Put another way, all Ethereum products can easily understand each other – this makes NFTs portable across products. You can buy an NFT on one product and sell it on another easily. As a creator you can list your NFTs on multiple products at the same time – every product will have the most up-to-date ownership information.

Ethereum never goes down, meaning your tokens will always be available to sell.