Given the fact that there are thin / normal weight people with type 2 diabetes, I think saying "ingestion of excess carbohydrates" is the primary cause is a bit

Given the fact that there are thin / normal weight people with type 2 diabetes, I think saying "ingestion of excess carbohydrates" is the primary cause is a bit misleading. You'd have to define "excess carbohydrates" as "enough to cause type 2 diabetes in that person", which leads to it almost being a tautology. There's still a large number of gaps in our understanding of the condition and it's causes.