This is what I think happened but its a long shot. Ok so as we all know nikolai, takeo and dempsey were all experimented on with 115 which caused them to suffer memory loss so let's say after the events of moon richtofen stayed in the aether but the other 3 time travelled back in time to a time that was before the time of origins and due to all of the exposure to the 115 powered equipment they lost their memory again but this time they didn't know anything about themselves which results in them never returning home or returning to the army and seem to disappear of the face of the earth. Know as we see in the video takeo tightens his grip when he sees the others which would mean that their memory has came back to them and them realising who each other is except for richtofen who is still in the aether in the future which would mean the young richtofen has no memory of what he or the others have gone through well that's my theory anyway. And just before anybody asks how the young versions of the three would know what the older four have been through I remember professor steven hawkins talking about that if an older version of yourself went back in time before a certain event happened that event would be in your memory in till it either happens or something or someone from that same time period triggers that memory. That's basically what my theory is based around
