How does increased sugar consumption cause diabetes mellitus?

For a long time increased sugar consumption was known as a risk factor for diabetes mellitus. But I always asked the question from myself how does it cause. So now I have one possible mechanism. Sugar is broken down in the body to glucose and fructose. As you know there is no question glucose increases insulin secretion. Now lets take an 8 year old child who has born with a defect of the pancreatic beta cells which secrete insulin. But the amount of insulin produced by the remaining cells may be adequate for his day to day life. What will happen if he consumes more sugar? The increase glucose level will put an extra pressure on the beta cells to produce more insulin. But now what will happen? The cells will try to secrete a higher amount of insulin and soon get exhausted. So now the child develops type I diabetes mellitus.
Now lets take a 50 years old person. Lets say he is genetically predisposed to insulin resistance. But pancreas can secret a higher amount of insulin and that person to overcome his insulin resistance. But when that person consume more sugar pancreas has to secrete even much higher amount of insulin so his beta cells will soon get exhausted and he will soon develop diabetes mellitus type II. Now if you have a family history of diabetes think about this before eat a chocolate.