You are conflating several issues. Yes, a creator presumably would have ways to cheat the system, for example by selling the same thing on different blockchains

You are conflating several issues. Yes, a creator presumably would have ways to cheat the system, for example by selling the same thing on different blockchains (as mentioned elsewhere). But eventually they would be revealed to be frauds and presumably the worth of their creations would plummet. To verify the identity of a creator is a solvable problem, though, and is also yet another issue than the "sell it multiple times" problem.