Because all of your ideas on extra-terrestrial intelligence are just theories.
I know for a fact that the Aliens that I know have been here since the super-continent Pangea existed... about 300 million years ago. They have always considered our planet a kind of "zoo-planet" where they don't interfere with our life... but they have.. they gave knowledge to the Mayans and Egyptians...
And, I actually communicate with them on a regular basis and I can tell, they aren't that smart... however, I'm really smart so they might still be smarter than the average human.
Erm no they have not theories. I've been in their ship and seen their records for their civilization. From early civilizations to getting here was the equivalent of 2500 years. This is less time than our civilization.
Well they have got past the problems due to relativity by using some form of quantum pairing that essentially transports the ship across great distances, although accuracy is limited so they still need to travel the last bit through conventional means.