The american SST was a bizarre beast. Looks like they were never really convinved that
speed was civil aviation future, and that the US Government just answered Concorde with a bigger project (because since 1962 Concorde was an ongoing, robust project; you never know, maybe Concorde might works, so we need an answer to it, even a paper one.)
At the same time however, realistic Boeing, Douglas and Lockheed CEOs knew the real future of civil aviation was
wide-body, not speed. Incidentally the CX-HLS was a perfect opportunity to develop wide-body technologies (notably large turbofans !).
Once the CX-HLS given to Lockheed, Boeing and Douglas imediately started their wide-bodies programs, resulting in the DC-10 and 747. Even Lockheed tried his hand at the wide-body game later.
Browsing the Flight Global archive it is clear that in the 60's noone really knew what future of civil aviation would be: double the 707 speed or double the 707 number of passenger ? The US government did not knew either, and decided to lock both options - supersonic through the SST, wide-body through the CX-HLS.
Clever people !