Our religious books, Quran and Bible, reflect some truth that will soon be revealed. It's a 40k+ topic which, to make a long story short, explains what a military intelligence team has to do with an ancient prophecy.
In fact they never left. They are just waiting for the right time to destroy the Cabal and cooperate with the Earth people again, like they did back in the days of Atlantis, before the Great Flood started the dark ages…