R1a is very much a minority lineage among Jews. It represents about 50% of the Levites, but only about 10% of Ashkenazi Jewish males in total, and is mostly Middle Eastern in origin.
See:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5668307/
Yes, I agree entirely. The point I was making is that most of it seems to have descended from just a single ancestor who lived only several centuries ago.
If that can happen, then a whole host of Levantine J2 migrants from the first millennium BC onwards could certainly have given rise to much of the 10% or so of the Iberian population that is J2 today.