An advanced civilisation, many, many times more advanced than we are, has managed to manufacture a craft, that can travel vast distances (it doesn't matter how it does it,hyperspace, faster than light, high fraction of light, the key is they've done it), that can sustain a life form(s) for the duration of the journey be it automaton, cyborg, whatever, that must have unbelievable computational power for navigation etc, as well as systems to provide protection against all kinds of heat, cold, radiation and goodness knows what else.
The craft arrives to Earth, and is flying along in the skies of New Mexico when lo and behold! It has a catastrophic failure (cause unknown but we're led to believe it was a lightning strike - note that even our aircraft can survive these but anyway we'll keep going) and crashes to the ground.
And most of us know the story from there.
We're then expected to believe that a Lt Colonel in the US Air Force is handed a few bits of recovered artifacts that are stored in a "filing cabinet" and told to dribble them out to industry to start a tech revolution.
Amd thus the optic fibre, transistor and whatever else revolution was born and we lived happily ever after thanks to ET, despite the fact that there is clear engineering and research evidence pointing to the fact that Bell, AT&T, Rand et al were working on these things anyway.
The whole thing is a load of bollocks, and there isn't any credible alternative.