I notice that more & more folks have diabetes. Is that mostly due to genetic defects, besides food, milieux, obesity, among other things?

Not really. More people are gettinfg diabetes because of sedentary life style and excessive eating genetic plays the same role as it did 100 yrs ago.
Primarily obesity. The dramatic increase in diabetes is directly related to the dramatic increase in our weights. Genetics havent changed but the rates of diabetes certainly has. Critical to eat regular healthy meals and exercise daily to maintain good health . At our current rates - 1 in 3 children will develop diabetes in their lifetime - it is a national crisis.