Why do people create nudifying AI tools?

Because they can. Because no law exists to stop them, and if such laws existed, they could not be enforced. And because it's profitable, which fact trumps all considerations of impact on society or harm to individual women.

The question we need to explore is why there is a market for such material. IMO it comes down to the nudity taboo, which sexualizes bare skin. And why? Such fakes are no doubt easy to produce because there is no mystery beneath our clothing. We all have nipples and genitalia, and they mostly look about the same. If we were not taught to hide those open secrets and feel shame to have them seen, no one would pay attention (or money) to purveyors of nude photos, real or faked.

As for deepfake videos, how are they different from real videos employing celebrity lookalikes? Porn will lose its profitability over time, I suspect, as amateur productions dilute and saturate the market. Because with sex, just as with bodies, the mystery isn't in what can be captured by a camera, but what lies beneath.

None of my comments are meant to minimize the anguish of those affected by this new depredation. I wish I could believe in hell, because any kind of justice would require those predators to suffer. But although the victims' pain is real, their shame is artificial--a social construct that has outlived its usefulness.