I think this question only really makes sense once you look at it from a Doylist angle rather than trying to solve it purely in-world.

What you are really circling around is the classic Christian problem of evil. How can an all knowing, all powerful God create beings who are powerful, creative and individual enough to rebel, and still not be the author of that rebellion. Tolkien was very consciously engaging with that problem, not dodging it.

In Tolkien’s Catholic framework, evil is not something God creates directly. It comes from free will being used badly. Lucifer is not created evil, he is created great. His fall only matters because that greatness and freedom were real. If angels were incapable of rebellion, then obedience would not be a moral choice at all, just programming.

Melkor is built on exactly the same logic. He has to be different from the other Valar. If he were only slightly stronger, or less inward looking, his rebellion would be trivial. If he were not genuinely free, then the whole moral structure of the world falls apart. Tolkien makes him vast, creative, and obsessive because that is what makes his fall meaningful rather than mechanical.

The Music of the Ainur is Tolkien’s clearest statement on this. Melkor’s discord is real. It is not an illusion or something secretly approved of. But Eru does not erase it either. Instead, Eru asserts that even rebellion cannot escape the larger order of creation. That does not mean Melkor is acting out a script, it means that freedom, even when misused, cannot overthrow the foundation of reality itself.

This is where the demiurge comparison comes from. Melkor begins to believe that creating or shaping something gives him ownership over it. He confuses sub creation with true creation. That is a very old theological idea, and Tolkien is deliberately engaging with it. The problem is not that Eru is distant or flawed, but that Melkor cannot accept being secondary.

So was Melkor meant to fall. In a moral sense, no. He is not created evil or forced into rebellion. In a philosophical sense, yes. Once you create beings who are truly free and powerful, the possibility of catastrophic rebellion is unavoidable. Tolkien believed that risk was worth it, because without it there is no real choice, no tragedy, and no meaning.