The suggestion in the paper is, pandemic and climate change (of course). "...the paternally inherited Y chromosome lineages show a complete turnover, linked to the movement of steppe-related ancestry that is also visible in other parts of Europe." Displacement, or maybe an earlier localized LGBTQ campaign of Y extinction led to invasion and domination by men from elsewhere.
With all the bad news these days these threads help keep a sense of sanity and proportion.