My personal opinion.
There is only one scenario that fits all of the facts. "Something" causes fat to be stored at the same time as damaging our organs and nerves. At the end of this process we have an overweight person with a damaged pancreas. It is illogical to think that fat causes diabetes since lots of people diagnosed are not fat. If they were predisposed to weight gain they would be fat as well but the thin ones only got the damaged organs and nerves.
What is the "something"? Whatever it is causes spikes of sugar levels which our naturally produced insulin is slow to deal with. Repeated spikes accumulate the damage and one of the organs damaged is the pancreas so a cascade failure begins.
Now that I study what I eat more than I did before I find that flour products raise my blood sugar most. I now have to avoid flour products unless I add fat to them to lower the GI.
Therefore, in my personal opinion, low fat products with flour in are lethal. My supermarket has rows and rows of such products which are made of flour and sugar. Some of them have had fat removed and sugar added to make them palatable.
One famous gravy has ingredients of starch and caramel, it has never seen a cow and is flour and sugar again. Put this on your meal and you have a surprise rise in your sugar.
I downloaded a chart from the WHO which showed that every region in the world has 10% of its population suffering from diabetes but not all of the regions have 10% who are overweight.