The ETs lived among them for many, many years because they didn’t die until they wanted to. Thus these beings were treated as gods and goddesses and these legends were born. Because they knew they would eventually leave and return to their homes they tried to pass the knowledge on to specific beings that they thought were capable of carrying it on. They also interbred with the natives to produce those who would have some of their abilities and be able to help the people after the originals left.
