^ The answer to those questions is fairly simple: because the process started even before Palpatine was granted "emergency powers" and declared the birth of the "First Galactic Empire." It all began while he was Supreme Chancellor of the Republic, and is shown through the evolution of starship designs, etc., during the prequel trilogy.
I suppose...but still. THOOUUUUUUSANDS of years?
Anywa...I also refuse to recognize the prequal trilogy as existing. I'm not even sure what you're referring to. Prequals? You mean like the Courtship of Pricess Leia? Or Heir to the Empire? Those happened afterwards though...
Oh, that brings up another point...Why are the CHISS involved in the Sith Empire? What? They are like an uber xenophobic group that hates being controlled. Thrawn was an OUTCAST from chiss society. Weird.
I'll still play my chiss Agent though.