Processed meats contain a LOT of salt. Salt doesn't cause diabetes, but it does cause water retention and high blood pressure, so is bad for people with diabetes.
As for sugar, they are on the list of foods they examined. What they found is that we're eating more French fries, so that turns out to be a bigger factor in practice.
Why is salt / bad influence for people with diabetes relevant in this context? Weren’t we interested in meat in relation to the rising global incidence of diabetes? Cottage cheese, shrimp, canned tuna and more also are high in sodium.
Worse, when you aim for that market customers start to want local, organic, grass fed, etc which drastically increases ingredient costs.
So the question is why it's hard to get even moderately low amounts of sugar, say <20% of calories from added sugar.
https://en.m.wikipedia.org/wiki/Renin%E2%80%93angiotensin_sy...
I think the salt consumption is a bit of a red herring and it's better to fix the metabolic syndrome.
This study seems to be the best we have. It’s observational and involved self reporting of diets.
https://journals.plos.org/plosmedicine/article?id=10.1371/jo...
It’s complicated too because nitrites found in fresh vegetables are strongly correlated with health improvements. This could mean that nitrites aren’t the problem, nitrites in the presence of animal proteins is the problem, or in the presence of fat, salt, etc. It doesn’t appear very clear to me.