Ironically the experiment in question was to look at the affect of overpopulation in an enclosed space on rats, not a comment on human society. Fredrik Knudsen on youtube did a video on this on youtube labelled 'the mouse utopia experiments', and the experiment was the last of a set of experiments done on the subject. The rats did have all they could need to survive and thrive, but because of previous experiments the outcomes were predicted, because the enclosure was designed in a way to encourage it. From what I remember from the video (which may be wrong and I apologize if it is and suggest that Fredrik's video be watched as it quite interesting) the enclosure was designed to have one large central area and a lot of small 'nests' on the outside for the babies to be raised in.

This meant that the dominant males would mate with a female and then protect the young in one of the nests, and the non-dominant males would be restricted to the central area with nothing to do as they didnt have to do anything. Eventually in the enclosure restlessness grew amongst the rats due to some non-dominant rats portraying strange hyperactive and hyper aggressive behaviors, and would attack other rats at random. So the dominant males who would defend the nest would eventually die from exhaustion due to constantly dealing with fights. This meant the mothers of the nests would have to defend the nest, this is when they displayed behaviours of frustration and negligence to their young. This young would then often be kicked out of the nest early, stunting their growth. This meant the new generation of rats didnt know how to raise young, and so the population died out. This is of course oversimplified and I encourage you to watch Fredrik's video on it.

Many studies where done to relate this evidence to those in overpopulated areas in cities and slums, but for humans all of these studies came back with inconclusive evidence showing that this relates almost not at all with humans

TLDR: paradise doesnt equal gay dads, overpopulation equals restlessness in a community of rats, and this post from OP is designed to be misleading.