Since refined sugar and industrial seed oils both entered the food market around the same time, it is difficult, if not impossible, to distinguish their effects by epidemiological means.
That said, however, there is a clear mechanism by which sugar and other carbohydrates cause insulin resistance, hyperglycaemia and insulinaemia, and Type II diabetes. The effect of seed oils is necessarily more indirect.
One of the concerns with the industrial seed oils is the large quantity they contain of polyunsaturated fatty acids previosly unknown to the human body. They are incorporated into cell walls and other locations and have negative effects. My understanding is that their connexion with diabetes is tenuous at best, with all due respect to Chris Knobbe and Tucker Goodrich.
In any case, the human body is not harmed by eliminating or restricting sugar, carbohydrates, and industrial seed oils.
ETA: It would be interesting to do a study comparing high intakes of sugar, saturated fat, mono-unsaturated fat, and polyunsaturates from seed oils. But I doubt such a study would pass an ethical review, since we “know” that arterycloggingsaturatefat will kill people.