They weren't adopted, they were inherited (in a way).
Consider that the Democratic Party is not a company or unified organization. It is a conglomeration (i.e., parts grouped together to form a whole for political goals but remain distinct entities).
Pelosi can finagle a voting bloc in Congress by her dealmaking, but the individual parts have the power granted them by their voters...and the leadership has little power to control them most of the time.
Whether the leaders of the Democratic Party like it or not, the Party is now infected with some deeply troubling individuals and their constituents.
Fortunately, this is not, for the most part, a problem that the GOP has.
The GOP needs to figure out how to capitalize on this situation and bring to the GOP those blocs (like Jews in the Dem Party) who now find themselves unwelcome at the Dem table.
Spot on, RoosterRedux!!