For those who are unfamiliar with the concept, a simulacrum is a copy of something that has itself become hyper-real and usurped the reality of the original. The canonical example is Disney World, which is a copy of Disneyland, which is itself a copy of many elements of Americana (Louisiana Bayou, the frontier West, Main Street USA, etc.) Disney World has eclipsed Disneyland in visitors, which itself has eclipsed visits to various small town main streets or the Louisiana bayous. You plan a family vacation to Disney World, you don't plan a trip to Bumfuck, Wyoming. Even though it's a copy of a copy (and a poor one at that), its reality has eclipsed that of the original, just because the original is hard to get to and kind of boring.
Similar with NFTs. Yes, you can make an NFT of the Mona Lisa and claim that you have the only one. Yes, you're a lying swindler and probably a bad person. But your copy is much easier to trade, move around, and store than the actual Mona Lisa. And just as there's only one original Mona Lisa, there's only one original NFT of the Mona Lisa, so your copy still has the same scarcity. As more capital comes onto the blockchain, your NFT is likely to acquire its own hyper-reality and become the Mona Lisa, and the original painting will be hidden away in a museum somewhere and disappear from trading.