Nadal's two Wimbledons are merely coincidental. He only won Wimbledon 2008 because of the psychological advantage of having crushed Federer two weeks earlier at RG 2008. His Wimbledon 2010 (def. Berdych) was a joke of epic proportions (second only to his famous USO 2010 flying circus).
Nadal always had enough game on slow grass to reach multiple Wimbledon finals, which is quite an achievement by itself, but calling him a grass court legend, getting surprised by him not winning Wimbledon after Wimbledon (like he does at RG), etc. is just silly.