Board Thread:General Discussion/@comment-5900631-20150108235930

Speculation:

In the past, the gems as a race came not to protect Earth but to conquer it. There was a schism, with some gems ( specifically Crystal Gems) feeling that conquering the world was the wrong approach; they chose to protect humanity instead. It resulted in a war. When the Gems were checking the Warp in Spce Race, they weren't hoping they were working; they were ensuring they did not so that the other gems could not return and resume their war of conquest.

Opinions? 