That would explain how they got so much data with a probably small number of compromised accounts. Ashkenazi Jewish people were relatively genetically isolated from the rest of Europe and started from a relatively small founder population. Genetically, then, they're all detected as distant cousins of each other using standard metrics.

This means a typical Ashkenazi Jewish customer of 23andMe has a lot more relatives than most other customers, and so they'd be able to view that many more profiles.