If I had to, and the writing was good enough to support it, I could get behind the Didact being a Captain Planet villain. But the writing doesn't support it.

Prometheans are weak. They're slow. They underperform compared to other Forerunner systems we've seen. They're comically, laughably underpowered, and their glowing holographic skull is a weak point that seems to exist to intimidate an enemy that can't be intimidated.

Which is fine, if it was just the Didact alone on this. But all the other not-insane Prometheans looked at the Knight's spec-sheet and said "Yeah, I should get melted down into one of those things. Totally worth my free will."

Then there's the fact that the Promethean weapons, which are so weak and inflexible as to barely qualify as a Forerunner's sidearm, are confirmed to be designs hundreds of years old by the time the Didact woke up from the Cryptum.

343i is writing the Didact as the villain of a saturday morning cartoon show, but they aren't that self-aware.