The E.T. relationship is a possibility, as I'm very open-minded about Extraterrestrials.
The problem is when it becomes a type of racism, i.e. as if non-Caucasians couldn't have possibly built that by themselves, so it must have been with help from outer space.
Unfortunately there are a number of Euro-centric and Ashkenazi-centric people in academia who always jump at the chance to try to discredit the achievements of melanated or darker-skinned people.
Speaking of which, some claim that the first Buddhist statues were Gandharan, which are said to have first appeared in the first or second century C.E.
However according to the above History Channel episode, the Ajanta Caves began to be carved around the second century B.C.E.
So it makes me also wonder if the "Enkay-Tenkay" Buddha carvings apparently found near Chandvad India are older than the Gandharan statues:
...the difficulty of the archaeologists still exists, if not in the fact of idols being ascribed to early Buddhists, then in the physiognomies, in the type of all these Enkay-Tenkay Buddhas.
They all, from the tiniest to the hugest, are Negroes, with flat noses, thick lips, forty-five degrees of the facial angle, and curly hair!
There is not the slightest likeness between these negro faces and any of the Siamese or Tibetan Buddhas, which all have purely Mongolian features and perfectly straight hair.
This unexpected African type, unheard of in India, upsets the antiquarians entirely. This is why the archaeologists avoid mentioning these caves.
When they can no longer keep a lid on it, it must have been "aliens".
Anyhow, I do think that some of the 'new age-ish' speculations on the Extraterrestrial-Tibetan connection could also be a possibility. Not because I would think that Tibetans aren't capable themselves of being very cultured without outside help; quite the opposite, as some Tibetans are perhaps one of the few people in modern times evolved enough to have regular contact with Extraterrestrials (of course I also think that there could very well be a handful of people from all races currently evolved enough to have contact with Extraterrestrials; yes, perhaps even some Caucasian Ashkenazis & Europeans)....