The original Dickstein 2015 paper [1] formulated diffusion as maximizing (a lower bound of) log-likelihood of generating the distribution, so there was some the

The original Dickstein 2015 paper [1] formulated diffusion as maximizing (a lower bound of) log-likelihood of generating the distribution, so there was some theory. But my understanding is that the breakthrough was empirical results from Ho [2] and Nichol [3] showing diffusion could produce not only high-quality samples but better than GANs in some cases. [1] https://arxiv.org/abs/1503.03585 https://arxiv.org/abs/1503.03585 [2] https://arxiv.org/abs/2006.11239 https://arxiv.org/abs/2006.11239 [3] https://arxiv.org/abs/2105.05233 https://arxiv.org/abs/2105.05233