It is really sad that some people become pet hoarders. I truly believe that most of these people love their pets very, very much, and are heartbroken if and when the pets are taken away by the Humane Society. Most of them start out with just a few pets, and then the cats have kittens, or dogs have puppies; and once that cycle starts, it is hard to stop it.
My son had a girlfriend that became a hoarder. For a long time, she just had her one pet cat, but then she acquired a pair of cats, and soon there were kittens. She loved the kittens, and didn't have any other family; so she couldn't bear to give them away.
Eventually, those cats grew up and had kittens, strays wandered in since there were already a lot of cats there, and she had put out several cat food dishes outside, plus more inside. The cats increased at an even faster rate; and she was still not willing to part with them, and by now, had so many that she couldn't afford to have them neutered.
Sadly, she also contracted cancer, died, and the county Humane Society had to deal with the cats. Many of them were not healthy, and had to be put to sleep.
The whole thing was terrible; but there was no way to stop her once she got so many cats, and became a hoarder.