Can someone educate me?

Hi all,

I have a cursory understanding of how blockchain networks work in practice as well as how NFTs are stored as data on said blockchains. But I was wondering if someone who is more educated than me on the topic could answer a specific question I have regarding NFTs in the future:

So I understand that the Ethereum blockchain is currently the most commonly used network for storing NFTs. But as I understand it, each new blockchain network that is developed is usually (but not always) iterative upon previous blockchains. So, for example, the Ethereum blockchain allows for more sophistication surrounding smart contracts as opposed to older blockchains such as the Bitcoin network. Therefore it's imaginable that several new blockchains might be developed in the future that essentially supersede existing ones such that they become much more popular with users.

So here is my question: if the buyer of an NFT has their ownership verified on a blockchain such as Ethereum, what is to stop someone creating a NFT of the same object (e.g. Nyan cat) on a new blockchain in the future, essentially stealing it? Is this impossible because newly developed blockchains use data from pre-existing chains (such as Ethereum) rather than starting from scratch? Because surely if a new ledger is developed that starts from scratch then all the data that is present on older blockchains that prove the ownership of a particularly expensive NFT will no longer be present thus allowing a new owner to claim the NFT?

I am guessing that my understanding is probably incomplete somehow on this topic but the thought popped into my mind when I heard about people spending a lot of money on a NFT Nyan Cat or the first tweet. Maybe in 10-20 years time or hell even 5 years when technology has progressed in a manner which we can't predict then maybe those NFT investments might be for nothing if the data held on current blockchains proving their ownership is essentially left in the dirt?