Their reasoning was that they were a warmongering race, just as they are now (lessons not learned). After they ruined Mars for themselves and everyone else on it, they were transplanted here by far, far more advanced aliens (guardians, literally acting as parents keeping clones of the baby Martian race alive in a spaceship in order to physically transfer them here) for another 75,000 year cycle of development along with all the other species of the human genome in order to learn how to play nice. We can all see how that has been going... As far as what they looked like, search for "pre-adamite skull" to see images of similar Anunaki-type beings. As far as when, the source material says 75,000 years ago, when our Grand Cycle began here on earth. Here's snippets from the source material: "The first of those to come here (earth) were brought from another planet in your solar system called by you the Red Planet, Mars. This planet’s environment became inhospitable to third-density beings." "The entities of the Red Planet were attempting to learn the Laws of Love which form one of the primal distortions of the Law of One. However, the tendencies of these people towards bellicose actions caused such difficulties in the atmospheric environment of their planet that it became inhospitable for third-density experience before the end of its cycle. Thus, the Red Planet entities were unharvested and continued in your illusion to attempt to learn the Law of Love." "The race is a combination of the mind/body/spirit complexes of those of your so-called Red Planet and a careful series of genetical adjustments made by the guardians of that time. These entities arrived, or were preserved, for the experience upon your sphere by a type of birthing which is non-reproductive, but consists of preparing genetic material for the incarnation of the mind/body/spirit complexes of those entities from the Red Planet."