I don't quite think it was that really. (SPOILER)Obviously the holder of the Elder Wand can be defeated otherwise the ownership of it would never pass on. Hence, Dumbledore could have simply disarmed Grindelwald or something and the Elder Wand would not have been as effective. While I don't think that would be the case, I think that the ability of the wand holder comes into it as well. Dumbledore was a pretty effective duelist and could have overpowered Grindelwald, I think be it through skill or luck.




