As we've come to understand insulin's impact on various tissues, the old "insulin helps glucose get in to the body's cells for energy" idea is so grossly outdated and wrong... But it is still the prevailing understanding of insulin in the general public, and shockingly, among too many doctors.
One effect of insulin is to stimulate the production of fatty acids from glucose in adipose tissue (as well as taking up plasma glucose). The theory -- gaining empirical support -- is that Insulin Resistance causes enormous increases in plasma insulin levels (hyperinsulinemia), which of course causes adipose tissue to go in to overdrive "making fat" from sugar in the blood that the liver and muscle are having a hard time absorbing due to IR.
So, IR, caused by T2, skews the body to storing carbs as fat rather than glycogen because of the high insulin levels. Worse, insulin also inhibits conversion of fat back into glucose, exacerbating the situation.
A lot of fat people very may well be that way not because they're overeating slobs, but because they've had T2 diabetes for years, but their pancreas is still able to counter their IR and keep BG levels normal, all the while doing so by turning up the glucose->fat conversion pathway.
This, BTW, makes weight control much more problematic for T2's, like myself, who are treating tight with insulin. The quantities I have to take to stay in a normal BG range, because of IR, are astonishing.
Low carbing for an tight-controlling T2 is really non-optional.