Merely eating sugar could not possibly cause diabetes all on its own.
For clearly, pretty well everyone in the world has eaten sugar in some form or other, and yet not everyone in the world has developed diabetes.
However, there is no doubt in my mind that had I not binge-eaten a large bag of sugar (in the form of a large bag of wine gums) on an empty stomach when I was in a HIGHLY STRESSED STATE 30 years ago, then I would not have received a diagnosis of type 1 diabetes shortly after.
No-one else in my family has any form of diabetes. And neither does any relation of mine that I know of.
To think that eating endless amounts of sugar could do one no harm, you would have to be a fool. Either that, or you might be economically involved in the sugar industry.