It's worth noting that the correlation held for total red meat consumption along with considering just processed red meats and unprocessed red meat separately
There are certainly some limitations of this study but it does align with the growing body of evidence suggesting a potential link between any red meat consumption and type 2 diabetes
Per-capita beef consumption has fallen by ~40% since 1976 (source) and rates of diabetes have nearly tripled since then (source).
So it doesn't seem like telling people 'eat less red meat' moves the needle on diabetes rates.
This study looks at the effects more so of replacing red meat with plant-based foods, not so much the effects of replacing it with chicken which is what the per capita consumption changes so more there
There are of course a number of other factors indeed that influence diabetes, yes