I don’t think you’re missing much...as you know there were 3 major Crusades, and these might have had a small part in reducing their numbers, but the Black Death likely had a larger effect.
No I mean I wasn’t including the earlier Crusades that might have affected the Sephardic Jews in Spain and Portugal, I was thinking Rhineland Jews would be of the Ashkenazis variety but according to this study they apparently didn’t exist back then (in 1096). Anyone have a link to the scientific paper, I’m also curious as to what statistical sampling methods were used.