If Dumbledore is all knowing why didn't he know that Voldemort would come to his grave and steal his wand?

I guess my question is that Dumbledore left all these clues to help Harry but didn't he know it was a high chance that Voldemort would come for his wand? More importantly, didn't the people who knew Dumbledore know how powerful his wand was so why did they bury him with it? The ending of the movie made me wonder...