Nixon continued the excursion for a long time after being elected (Promising to end the draft in ‘69 if elected, never happened that year). Intel was probably the primary reason because militarily we were extremely passive/only played defense in SV, there were “US Spooks†all over North Vietnam doing Intel on the USSR/China. Knew a guy who would deliver supplies in NV right in the middle of a jungle. Places he could go are described as concrete structures/some mansion and plantation types/ filled with wall-to-wall computers.
Nixon had a knockdown dragout effort in 71' to keep the draft going in Congress for another 2 years and won.
So much for campaign promises...