There is an interesting quote on Billboard from an interview with a board member:
You'd be amazed if you watched these juries at work; they take seriously every bit of work they consider. In this case, I don't know specifically what the piece was, but in this case they were considering a piece of music they felt had hip-hop influences and said, "Well if we're considering a piece of music that has hip-hop influences, why aren't we considering hip-hop?" And someone said, "That's exactly what we should do." And then someone said, "We should be considering Kendrick Lamar" and the group said "absolutely." So then, right then, they decided to listen to the entire album and decided "This is it."
Seems very 2018.