Insulin resistance is a quality of the cells in your body which cease responding to insulin at their receptors. So higher levels of insulin fail to reduce blood

Insulin resistance is a quality of the cells in your body which cease responding to insulin at their receptors. So higher levels of insulin fail to reduce blood sugar levels. This is the hallmark of T2D. You are confusing this with beta cell function, which also becomes impaired in many T2D people, where the islet cells become damaged, insulin production is subsequently impaired as well, this is a later stage effect in T2D progression. T2D likely manifests from prolonged energy surplus leading to oxidative damage to cells and accumulation of excess fat stores, particularly visceral fat stores in the organs - the cell damage and overfull visceral and sometimes subcutaneous fat stores both lead to hormonal and epigenetic changes and directly to insulin resistance. That's still oversimplified, but it's a useful model.