Well technically, yes.
But I don't believe "overeating" is a 'primary' cause of anything, it's a symptom. Given research, most likely of combined chronic malnutrition (both in nutrient deprivation and in acquired toxin). Telling people that crappy food is good and good food is dangerous and they eat "too much" merely results in people making the malnutrition issue WORSE in both categories.
But does "your food intake" cause/contribute to T2DM? Yes, of course it does, and to obesity and probably every other disease that isn't 100% genetically acquired. The very fact that people can reduce and even completely revert T2 through eating habits ought to demonstrate that well enough and there are tons of people who do.
The problem is the ADA is filled with advice about how it's perfectly fine to eat candy, sodas and pie as long as it is "in moderation" and with insulin to compensate. The very metabolic problems that give people T2 in the first place, never mind the standard American diet, never mind a diet even slightly geared to low-cholesterol/fat, are unlikely to result in people eating sugar/carbs "in moderation."
Regarding people's beliefs though, I'd say the problem is the wrong things are considered the bad guys. Yes, all the health agencies will say that you should not live on junk food, of course. Not even the worst ones recommend donuts and snickers, but they do recommend whole wheat bagels and plenty of fruit, which if you're looking at carbs+sugar+grains is going to affect body organs (and brain chemistry and human cravings) just as well.
As long as the powers that be are telling people to avoid meat and eggs and eat lots of grains and stick to PUFA fats, they are essentially recommending a diet destined to give most people, without "a pancreas of steel" (as I think it Peter at Hyperlipid humorously refers to it), T2 diabetes eventually.
As for fat diabetic people eating horribly, that clearly doesn't help. But I know that when I first gained a ton of weight very fast (~200# in 2 years), and then went on a diet, I did The Perfect Diet(tm) according to all the sources of info I had at the time -- low protein, super low fat, high in carbs, high in grains and fruits, high in morning exhausting aerobics. It took a month to not really lose weight, during which I felt more horrible than I ever had in my entire life. I was not only freezing and beyond-exhausted and ravenous the entire time, I was verging on homicidal and clinically depressed. I knew there was no possible way I could live like that. Not even a little.
So I said f---- it, and I ate whatever I wanted, which of course was profoundly the wrong decision, given by that time my body was already screwed up. So for years I varied from not eating for 1-3 days (as Jack Kruse pointed out, the superobese have the same leptin profile as anorexics) to eating in compensation for that and nearly always badly. When I would sometimes attempt to simply "improve my eating" I would shift to vegetable oils and grain foods and fruit smoothies in my deluded notion this was so much better for me than just having a steak, which only made the primary malnutrition issue even worse, in a spiral. I'd not heard of LC and didn't know any bodybuilders or life might have been different. At least nowdays I think most younger people are more exposed to these ideas.
Anyway -- I'm guessing that when people behave like that, it's less that they don't care as that they feel like it is hopeless. They try to maintain the advice they're given, fail miserably, feel horrible, and finally give up. Unfortunately instead of giving up meaning "becoming more moderate" with whatever advice they were trying to follow, it usually means just throwing every bit of good idea to the wind. Sad, really. But sometimes predictable.
I have talked with many people over the years who were overweight and diabetic. When I talk with them about LC and about how I've known many people with T2DM who were able to reduce if not completely reverse the condition through food choices, eventually their response is simple: "I could never give up breads."
There you have it. Bread is the drug of today.