Why does the pancreas of a diabetic not make insulin? i know it doesn't produce insulin, but why?

Diabetes : Diabetes is a serious medical condition manifested by high blood sugars and poor Insulin performance. Sustained high blood sugar triggers the "beta cells" in the pancreas to produce insulin, however over time sugar is pushed into the body fat/tissues/muscles and as the body continues to be in a hyperglycemic (high blood sugar) state, the body is unable to control the sugar levels with insulin. Overtime, the beta cells in the pancrease (pancrelipase) become over-exerted, but still do not lower the blood sugar levels. Once these cells become 'exhausted, administered Insulin injections become necessary yo control the blood sugar.

Beta cells: Beta cells in the pancreas are the ones that produce insulin. These cells get wiped out by an autoimmune response - that means that the person's own immune system attacks and destroys these cells. We still aren't sure what triggers this attack.