No, we don't know. "Genetics" in this case is just another way of shrugging and saying, "Don't know why".
I could get you a detailed explanation of EXACTLY what happens in the human body as it grows obese to cause it to develop diabetes. But no one as yet can give you a similar explanation of why a BLACK body is more likely than a white one to get diabetes under the same circumstances. Simply saying, "genetics" at that point is like saying, "because he's black". Thanks, Captain Obvious, but that's not helpful.
I get that you are observing the dictates of political correctness, but it is decidedly foolish to believe that all races or people must be equal. Nature does not worship at the alter of PC even if you do. Genetics dictate a great deal of a person's intelligence and health and ones race dictates ones genetics Madam Oblivious. Save that for snowflakes.
You can think you "get" whatever you want. Far be it from me to EVER try to force complex, intellectual thought on people who aren't equipped for it, and I'm well aware of how allergic the two-digit IQ crowd is to facts and reality.
Since you're clearly incapable of even noticing the words I'm actually saying, and since doing so would only make it harder for you to pretend I am the eeeevil PC opponent you came here determined to find (even if you have to create it out of your own imagination), and since I make it a policy not to converse with ignorant bigots, you are dismissed.