The plague may have caused the downfall of the Stone Age farmers

[Warpy]

5. Disease was rampant and dying in infancy was common

While hunter-gatherers also had high infant mortality, the adult remains showed them to be in much better overall health than their contemporaries who had turned to farming.

Farmers might eat more year round but the diet was also a lot more restricted

In addition, I don't think hunter-gatheres were as hungry as you seem to think since meat and fish would have been smoked and dried and grains harvested when patches of them were found, berries dried, and legumes harvested when they had dried out enough. All of those foodstuffs would have been light enough to transport via travois as the band moved to a place where they could winter over, often an aggregation site where other bands would assemble, also. In spring, when animals would start to move north, people would follow.

Both lifestyles were tough but both supplied adequate calories to continue. However, the skeletal remains tell the story of increased disease and overall poorer health and increased disease among farmers.