Team XLR - V

I lost power steering some time ago but continue to drive the car and just muscled through.

Not knowing the history of the car I decided to replace the power steering pump. What I discovered when I was finally able to get the pump off the car shocked me. The female receiver for the pump drive looked as if the teeth had been stripped. Now I am in need of a new power steering pump drive and an easier way than the thing came off to put it back on.

While searching for this new part I would be curious to know if anyone might know what would cause this to happen?