Disease is nothing to sneeze at! One new virus could quite possibly have wiped out an entire population (as it did so often in more recent human history). The end of the glaciers was the perfect condition to increase mobility and thus disease vectors.
In fact, this is so inevitable we'd have to explain why it couldn't happen, before speculating on less-likely scenarios?
"we'd have to explain why it couldn't happen, before speculating on less-likely scenarios"
The colonization of Americas is the perfect counter-example for disease wipe-out explanation. Pre-Columbian American population had no immunity whatsoever to a bunch of serious diseases (some of which managed to become pandemics back in colonizer's homelands), diseases that have accumulated over millennia (since the last Bering overland/over-ice human crossing)! You'd expect that on first Columbian contacts there should have appeared a pandemic so severe over the whole Americas that after a few years the Europeans should have had no one alive to encounter! Not only they still encountered, but long after the first contact they also had a hard time dealing with local resistance of underdeveloped tribes which had worse medical conditions than what was to be had in ancient Rome! Not only that locals haven't been wiped out, but they managed to contribute in a large quote to nowadays's Ibero-America's genotype despite the European settlers' massive migration! So yes, I think it's enough reason to consider the disease a less likely cause for a continental scale wipe-out (which is what the article was talking about).
A perfect example! Estimates are that 100 million aboriginal Americans were wiped out by diseases brought by Europeans. Most of the population of North America succumbed. The largest dieoff in human history.
We'll never really know the depth of native culture pre-Columbian because of this.
In fact, this is so inevitable we'd have to explain why it couldn't happen, before speculating on less-likely scenarios?