How does Google do this legally at all? Can I just download and redistribute any and all content I find on the net, and then present it as if it's the original?

How does Google do this legally at all? Can I just download and redistribute any and all content I find on the net, and then present it as if it's the original? More specifically, how do they not get sued into oblivion for copyright infringement? They are after all redistributing content they are not licensed to redistribute.