The Beaker people and their replacement of Neolithic DNA - is this remembered in Irish myth?
https://www.mythicalireland.com/MI/blog/ancient-sites/the-beaker-people-and-their-replacement-of-neolithic-dna-is-this-remembered-in-irish-myth/
Prehistoric Genocide in Ireland?
https://www.ucl.ac.uk/mace-lab/genetic-ancestry/guff_documents/Genocide_in_Ireland.pdf
“The newcomers replaced about 90% of the existing gene pool in Britain in the space of just a few centuries. The reasons for this are not known, but it is thought factors such as climate change, disease and ecological disaster might all have played a role.”
No honest intellectual thinking there, because an equally plausible explanation was (a) the “beaker” people were very successful and (b) success can lead to more abundance (c) and greater population, which (d) can lead folks in the expanded population to seek new lands; and (e) which introduces their customs and language to the new lands they settle in. That plausible scenario requires no climate change or ecological disaster - just some folks who were very successful and more so than the “natives” of lands they move into.
My first thought as well.