Why is my Cadillac DeVille D Elegance still overheating after I changed my water pump, the water pump pulled, the water pump belt, the tensioner, the radiator, all radiator hose and Took out the thermostat

Hello, the clue here is that the overheating happens when idling - not when driving. Because of this, it sounds almost certainly that there is a problem with the cooling fan. Unfortunate you did all that other work which was likely unnecessary. I wonder if it would have been less expensive to seek guidance at a local shop, having testing performed and make needed repairs? Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops