since so few 2nd rounders make it to the NBA and stick, it's not surprising that Williams didn't pan out in his first go-round. There is enormus pressure on rookies, especially one like Williams who was drafted by a veteran World Champion team.
The D-league and overseas give these guys a chance to improve and earn a spot (like Bowen from the CBA) or maybe an alternative career location where they can still play for pay.
I never understood all the hate directed at this kid just because of his limitations. The best estimate of his playing ability which determined his draft position was the responsibility and choice of the FO and coaches.