dumb enough to think that studies published in top-tier journals like Nature might not have accounted for even the most obvious confounding variables
That's because they don't. Survey based studies especially so and then their little biases get amplified when collected into meta-studies.
For processed meat vs other food studies, I haven't head of any research that did it properly. As one example out of many, how do you eat a hot dog? How do most people eat hot dogs? Do you microwave it, cut it with a fork, then eat it piece by piece? Do you grill it until it's half burnt, wrap it in a bun then smother it with ketchup and mustard? In a food study, both ways of eating a hot dog count as eating processed meat yet the wrap and dressings people use often outweigh the actual meat they're eating. 1 hot dog = 120 cal (w/1g carbs). 1 bun + 2 servings of ketchup = 150 cal (w/31g carbs). The two are not equivalent yet food studies treat them as identical.
Then lets use common sense. How does meat lead to type 2 diabetes? The pathway for eating carbs leading to diabetes is easy to understand. What is that pathway for meat? All these questionnaire studies claiming meat is bad yet not any of them show how the meat causes damage. There's a ton of other research directly looking at how carbs damage your body and blood vessels. There aren't equivalent studies on meat because at the cellular level meat isn't the cause of that damage.
However the slight increase risk of colorectal cancer for processed meat is true due to the unnecessary use of nitrates. That bit of science is well documented too. Also documented is the increase of bowel issues due to fiber intake which dwarfs that cancer risk. As always, the side with the biggest marketing budget wins the public opinion.
If you want a better research group, look at the people eating the carnivore diet and compare all their health problems to other diets. That'll give you a better comparison with the problems of eating significant amounts of meat.