I can't speak to this specific DA, but party affiliation for positions like this one (and judges) is often irrelevant. They often run on the ticket of whichever party is most popular in a given district. Also, "tough on crime" is a generally winning message in these elections.
Within 6 months in 2018, the Minneapolis police arrested 47 people thru sting operations against *small-scale* *marijuana* sales. 46 were black. Freeman's office chaged all of them with felonies. Which is to say, he isn't the person who'll fix systemic racism in law enforcement. https://t.co/ttR0EzLta8