"50 years ago when the first Citation came out, it had to have 2 pilots by law because it was a jet...all 300 and something kts of it."
Not so. "
The Citation II/SP is the single-pilot extension of the Citation II. Its first flight was on January 31, 1977, and it was FAA certified in March 1978."
The only difference was the SP was certified 12,500 pounds max weight.