"Awful rappers" don't make it to the top of the charts, especially unsigned ones. I think it's safe to say your opinion on his abilities to rap are in the minority.
Awful rappers make it to the top of charts on a regular basis. Rap music sells because of the beat and, to a lesser extent, the hook. Macklemore isn't awful, but as rappers go he's nothing too special. His hustle should be admired as should his ear for beats.
topping a chart requires a plurality not a majority. 98.9% of people could hate him with every fiber of their being and he'd still top, as long as their votes were evenly distributed across 99 other songs.
I don't disagree I just don't see how this means he could be "awsful". I think "awful" is an awfully sensational word for describing someone who is famous, playing on the radio, makes it to #1, and isn't even signed. Awful is me trying to rap.