There is one explanation that the interdimensional beings people call “aliens” were first seen in an underground base.
It was explained that the experiments that were taking place, opening up electromagnetic portals, was like casting a net out into hyperspace and materializing whatever was in proximity.
One of these explanations insists that the beings were grounded here as their craft was not designed to depart from the material environment of the under Earth base. It was said that these beings then remained until the required technological modifications could be made with provided materials.
There is an another explanation that these beings found an interest with the planet and decided that there would be an ongoing integration of technology and information.
This could be taken three ways. That society has been given tech by ‘aliens’ who’s intentions are to dominate. That society has been given tech or knowledge by ‘aliens’ who want to assist. Or that the entire situation is a fable. With the explanation that it is a fable comes the twist of whether this is to subdue people from the truth or to assist in knowing the inevitable.