They didn’t get genetic raw data of anyone beyond the 14K, they got family relationship information. Which is an option you can turn on or off, if you want. It’s very clear that you’re exposing yourself to other people if you choose to see who you’re related to. It doesn’t expose raw data and it doesn’t instantly expose names, just how they’re related to you. (And most of the “relations” are 3rd to 5th cousins, aka strangers.)

Hackers used the genetic ancestry data of the 14K hacked users and their “relatives” connections to deduce large families of Ashkenazi Jews.