As I read about the subject, it sounds like they didn't have a good source of those vitamins, as most of the land that makes up Germany is iodine deficient- so

As I read about the subject, it sounds like they didn't have a good source of those vitamins, as most of the land that makes up Germany is iodine deficient- so even foods supposed to be high in iodine, are not. So the way they found was to iodize their salt. The information seems to be spotty though.