There are a lot of variables such as monosaccharides vs polysaccharides with sugar, (in all its different forms and structure) fiber content in the carbs, etc. High fructose corn syrup is also starting to be seen as a major correlation with diabetes as well.
Diabetes (Type 2) is caused by constantly high blood sugar (glucose) rates and there is an undeniable correlation of first world country diets and increases in obesity followed by a increase in Type 2 diabetes.
Constantly high blood glucose levels result in the body thinking it has too few receptors that stimulate insulin and thus overproduces them resulting in higher productions of insulin burning through glucose too fast. This is what results in “low blood sugar” or hypoglycemia.
Your body can compensate for short bursts and durations, but it is the long term that causes the disease.
So yes, high carb diets can result in obesity and furthermore diabetes BUT you have to consider though the activity level of the consumer, the type of carbs, the frequency of intake and portion sizes.
Eating a sweet potato with 3.5 grams of sugar per ounce for breakfast, lunch and dinner and burning it off working in between probably won’t cause diabetes. (They also are though to have a fiber that helps lower cholesterol and blood sugar in moderation too) Eating loads of processed foods high in refined sugars and simple carbs constantly, doing very little work if any at all day in an day out just might.