It might be easier than that. Data Broker companies are the ones that run those stupid "Which LOTR character are you" or "What color are you" quizzes that are popular in some social media circles. They do it to slowly build psychological trait models of the people taking the quiz. This allows them to sell that information to marketing companies.

Access to that kind of data would help an AI determine the people that are more susceptible to manipulation. Add in records on health care, as you mentioned, and information on debts and you have data that can help an AI gather as many human minions as it needs.