If it were attributable solely to Protestantism, the black vote would not be Dem.
No, no one can explain anything about blacks and religion, or politics, or many other things in regards to the black relationship with their churches and religions, we do know that even they cannot dilute the overall Protestant vote enough to make it like the overall Catholics vote.
The wider experience of 160 years of history and with what happens to Hispanics and other minorities is more revealing.