I don't want to say my experience is that of everyone, but I recently was diagnosed with T2D when I gained weight due to COVID-19 interrupting my exercise routine. Dropping weight has brought my A1C levels back in line in the past, then when I gained back some my A1C levels went back up. I'm not particularly prone to weight gain, but getting much into the overweight range kicked me into a diabetic A1C range. My father has similar characteristics, with even a health weight and diet leaving him with pre-diabetic A1C levels. But then in contrast, my mother and her mother were obese for decades without a smidge of diabetes. Lots of genetics going on there.