He's got a fairly high salary for an 18yo because he's got near maxed big man skills. Salary is the only determinant of the draft scouting ratings.
One thing I've found over time with the game is that extreme height players (6'1 or shorter, 7'0 or taller) appear to have a weighting toward skills specific to their height. And the draft does give you options to scout skills you feel are critical, if you want to try to avoid getting pure donkeys like this.
The stamina and FT roll is pretty unlucky.