Was it the entire population or just the males? At this time there was a worldwide phenomenon called the Neolithic Y chromosome bottleneck in which 95% of Y chromosomes disappeared.
Could this mean just that 95% failed to reproduce?
The fact that we see this disparity between the sexes means that this wasn’t a disease based takeover like it was in the Americas.
If I was slaughtering the hunter gatherers I would only kill the males, the females would make good wives for my new settled civilisation. And giving the men wives would enable the civilisation to maintain stability (incels will stab up the longhouse)