I have heard several things. First the looking upon Noah’s nakedness has been conjectured to be Ham looked at Noah’s wife, his Mom, in some illicit way. That still doesn’t explain the curse on Canaan. Second, a theory is that when Noah saw Canaan, he bore some marking of the hybrids. For instance, the 6 fingers of giants in the Americas. And Noah knew there was a curse there. God blessed Noah and his sons. A third conjecture is that since God blessed them man couldn’t curse Ham so he skipped and went to Canaan. I’m not sure what the answer is there.
Now THAT is a Smithsonian exhibit I'd drive a LONG way to see!