If he wanted to go in last year's draft, he'd have had to do all the combines on a broken foot and hold off surgery until after the combines were complete. That wouldn't have helped him much.
It was the smart thing for him to do to come back and try to play a year of healthy football. His draft status wasn't going to be great last year with a broken foot. It may not be great this year either, but he had to take the chance to come back and see if he could play healthy and improve that status.
Obviously, he's just another one of those big guys that is forever going to have foot problems. It sucks for him, because healthy he's a definite first rounder, maybe even a Top 10 pick. With the injury issues, he's going to lose a lot of money.