Weight loss for diabetes is relevant especially for type 2 diabetic patients whose insulin has become resistant. Hence making more sugar levels be added to the bloodstream.
Secondly, being overweight puts you at risk of getting diabetes since, as explained above your insulin reaches a point that it cannot effectively regulate the sugar levels in your bloodstream.
With increased insulin resistance, it becomes difficult to regulate blood sugar levels hence increasing the risk of diabetes. Losing weight for diabetic patients also helps them move freely during their day-to-day activities and while doing exercises. These activities ultimately contribute to their blood sugar control.