Based is a slang term that originally meant to be addicted to crack cocaine (or acting like you were), but was reclaimed by rapper Lil B for being yourself and not caring what others think of you—to carry yourself with swagger. Based has been appropriated by the alt-right online as a general term of praise, as if “un-woke.”
-Dictionary (Slang)
Not fully sure if this is the actual meaning but it makes sense.