I think this situation says a lot about the nature of human desire, not just the fact that a few people were ingenious to come up with the idea of diffusion models. A lot of ingenious inventions are relatively boring when exposed to the broader populace, and don't hit on such an appealing latent desire.
What will this say about the limitless yet-to-be-invented ideas that humanity is just raring to give itself, if only someone would hit on the correct chain of breakthroughs? Would even a single person today be interested in building a backyard nuclear warhead in an afternoon, and would attempt to if the barrier of difficulty in doing so was solved?