IMO it's not a problem of overpopulation so much as it is of abundance of resources and comformity.
Mice utopia didn't even get close in population to how many mice can exist in a confined space while retaining their instincts, it fell apart because everything was abundant which led to erosion of survival instinct as it ceased being necessary for, well, survival.
It's why India and China can generally be seen as conservative societies despite insane population numbers, because conservatism, family values, a social structure makes life easier and safer, resources easier to obtain, in the west people can count on their government to fulfil basic needs, you can go without any job and you won't starve even if you don't have a family unit to fall back. Hell, starting one can be argued to be a liability as it is far easier to go through life alone doing whatever the fuck you want these days, all you need is a brain.
I believe we can observe that with Jim, ever since he got big on Patreon he started becoming more and more insane compared to what you'd expect of a man his age, all his needs are taken care of and he doesn't really need to do anything for it, whatever internet cliques he attaches himself to he doesn't attach to for support but for masturbatory asspats.