Later on of course. But if you take a look at just the minstrel era, these were highly celebrated artists performing at a time when catching a show was far and few in between, if ever for some. These artists were indeed understood to be intelligent and talented for their accomplishments, they were rock stars per say. Yet they did black face.
Could they have been trying to make the perception of their own intelligence and talent also be associated and extended to blacks? Music has always been one of those color blind fields of art and entertainment. There is no color or ethnicity, only talent and skills which have always been appreciated by fellow artists and fans of all backgrounds.