Diabetes II is genetic.
It’s genetic in the sense that some people are probably more prone to developing insulin resistance than others. Most of the time, if they start soon enough, Type II can be controlled with diet and exercise.
My wife is a Type I, juvenile onset; my mother was a Type II. If I quit exercising, ate whatever crap I felt like, and let my muscle mass waste away, I would be diagnosed as a Type II Diabetic within five years, almost guaranteed.