How is possible that monks memorised 10.000 sutras?

According to Wikipedia , in the Sutta Pitaka of the Pali canon there are 10.000 sutras. According to tradition, Ananda recited by heart all 10.000 sutras after the death of Gautama and they have been memoriesed and recited regularly by monks, for many centuries, before they were written down. So my questions is: how is it possible to memorise and recite regularly 10.000 sutras? Is it realistic to think it happened like that or is there another explanation about how the sutras have been transmitted and written down? I hope the question is clear. I’m asking this because if I try to image today’s monks memorise and recite 10.000 sutras it seems something out of reality. My guess is that only very few people would have the ability to do that. So I struggle to imagine how they could have done it for centuries. But maybe I am missing something and there is an explanation that I cannot see.