If everyone starts that doing we're going to put the pharmaceuticals out of business. There'd be riots!
Type 2 diabetes isn't caused by diet. Certain diets can increase the risk of Type 2 diabetes, but it's not a foregone conclusion, and it's not uncommon to develop Type 2 diabetes despite an otherwise healthy diet.
It is not very uncommon, and in fact the most recent (last ~decade of) research has actually caused us to question the extent to which people genetically predisposed to diabetes can mitigate their risk through diet and lifestyle choices.
Neither were significantly overweight when they were diagnosed. In fact, my Dad has been trim for decades, and while I don't see my uncle often, he was always thin and very fit-looking when I have seen him.
There _has_ got to be a genetic component independent of lifestyle and diet choices. Me? I have no excuse. I'm overweight and not active and I know I need to change that.
edit: Didn't proofread.