Why does your car overheat after car runs to operating temp and then you turn car off and back on?

Why does your car overheat after car runs to operating temp and then you turn car off and back on?
When you shut off an engine, the water pump stops flowing h20 plus antifreeze through the engine block and radiator. All of that extreme heat settles into the aggregate fluid. This can cause the engine to over heat the fluid and boil over. That is the reason you do not go out and take off the radiator cap. You could be severely burned or scalded by the hot fluid. That fluid has to be pumped constantly to keep the engine cool. The electric fans should cut on and help cool to some degree. Too, while you are driving on the road, the air at 30 to 60 miles per hour will help cool as well. When the air and the water stop flowing. Heat will build up.