university of North Carolina
You can get drafted into the NBA from Canada similarly to the way that players from the USA get drafted. Several players from Canada have played in the NBA such as Steve Nash, perhaps the most famous.
I would assume it is because there is a higher probability of them being drafted into the NBA than there is for football players to be drafted into the NFL.
60 players were drafted into the NBA in the 2008 draft
Kentucky 5 of their players (john wall, demarcus cousins, Eric bledsoe, Patrick Patterson, and Daniel orton) were drafted
There are 30 teams in the NBA, therefore, 30 players were drafted in the first round.