They started this experiment say, 20 or 30 thousand years ago, and have been making repeated visits to our planet to infuse us with some sort of gene-splicing material. That’s why there were so many different people, from early ape-man, through Neanderthal to Cro-Magnon to modern Homo sapiens. Each jump in the evolutionary tree was another genetic test.
At one point, they decided to go with one race, let’s just say the Jews, maybe because they were the most cohesive, since they don’t intermingle much with other races. All the accounts you read about in the Old Testament are just the scientists trying to make sure that their control group doesn’t get destroyed.
Let’s say these alien people have evolved to the point where they can communicate through telepathy, and manipulate the elements around them using their minds. Let’s say you’re a shepherd named Moses in ancient Egypt, and you “hear” a voice telling you to do God’s will. Maybe this voice tells you his name is “Yahweh” (which could be the actual name of the lead scientist, for example), and you must do things for him and protect your people. When really what “Yahweh” wants to do is protect his experiment, and continue to get “funding” for it! It goes on and on through the years.
They tried to accelerate the process too much by making Mary pregnant with Jesus. They impregnated her with half the DNA from one of their own. That’s why Jesus was able to do all those things. He grew up knowing he was somehow different than the rest of the kids (as he would be if his DNA was half-alien), and at some point in his life, he got a “calling” to go out by himself. (Once again, “Yahweh” communicating into his mind)
Maybe at that point, this race revealed themselves to him, and showed him some of the marvelous things he could do, being half-them. They show him how to help his fellow man, since they were a benevolent people, and thought they were doing all this to help us move closer along the evolutionary ladder toward them. He was able to know what people were thinking, when power went out of him, make food miraculously appear, heal sick people, etc. All because he was half-alien, from a 500 billion year old race. But, all that he did was not understood; he was far too advanced for the people of that time, and so he was killed.
Maybe he didn’t really die, or die as we know it, but on a cellular level went into some sort of hibernation until his body could regenerate. At that time, maybe the results of his regeneration were that he became more like the race of aliens from ??? (maybe Alpha Centauri, it’s the closest star), and they couldn’t allow him to stay or it would blow the experiment. He was physically taken from the planet.
That’s why, in the 1st book of Acts, you read of him “ 9After he said this, he was taken up before their very eyes, and a cloud hid him from their sight. 10They were looking intently up into the sky as he was going, when suddenly two men dressed in white stood beside them. 11"Men of Galilee," they said, "why do you stand here looking into the sky? This same Jesus, who has been taken from you into heaven, will come back in the same way you have seen him go into heaven."
Those two were other members of the scientific expedition making sure that the illusion was maintained.
Maybe they will be back in another 1000 years or so. That’s not so long to a race that lives 500,000 years. Maybe they’ll return, with Christ, since he is now a lot like them, when they think we’re ready to accept the idea that we’re not alone.