Now Camp One has just recently arrived, and they are doing their investigations from square one, so to speak. Camp Two have been around a long time. They know what humans are like a lot better than we do in many ways. They certainly seem to have better ability to deal with certain kinds of illnesses, and surgical techniques than we have. They are also the ones who induce a feeling of friendliness on the part of the people they pick up.
People think of themselves as being picked up by old friends.
Now, of course, this may be psychological manipulation. It is nice to have them do that kind of psychological manipulation. Furthermore, the Camp Two aliens will actually provide medical help and other kinds of help on occasion. Not the lizard aliens. The Cocoon sort of thing.