A prolapse is just another name for a hernia. As the Dr says, they happen.
It is true, a uterial hernia is much more common in women after child birth. But that is irrelevant really. Perhaps the only rerason we even think about it is because we call one a prolapse, the rest hernias.
It might be unusual for it to happen in a post op woman. Perhaps a comparison would be, a car fan belt breaking, just after you've had it serviced. But these things do happen.
Repair of a hernia/prolapse is routine. Just don't go thinking of moving any furnature around, or carrying any heavy shopping for a while.