This article addresses the connection between diabetes and cardiovascular disease:
The answer comes in understanding about insulin resistance. Insulin resistance typically precedes diabetes by many years, maybe even decades.
High insulin is inflammatory. This is what contributes to / causes heart disease.
They also know that even slightly elevated blood glucose, still in the "prediabetic range" is associated with heart disease.
How to address insulin resistance? Lifestyle for sure. Lower carb, low processed floods, low sugar, exercise, weight management, stress management.