Not enough technology in the late 60's?
So we had -
Viable submarines enabling humans to routinely operate in an airless hostile (and high pressure) environment over 100 years ago.
Flying the Atlantic just under 100 years ago.
Rockets (V2) reaching altitudes in space and dropping 2000lb warheads on London from 200 miles away over 70 years ago.
USSR reaching Earth Orbit 60 years ago.
USSR/USA sending man into Earth orbit early 60's.
Manned Moon landing 1969.
What technology didn't mankind have?