It wasn't so crystal clear then. I'm assuming the documentary you saw was Nova's "Battle of the X Planes". Recall that a Navy requirements change made Boeing's

It wasn't so crystal clear then. I'm assuming the documentary you saw was Nova's "Battle of the X Planes". Recall that a Navy requirements change made Boeing's design overweight, so it never performed any STOVL operations in its full flight configuration. Lockheed Martin had an aircraft with enough margin to do a short takeoff, supersonic dash, and then land vertically, all in the same trim. So the DoD had to choose between Lockheed, which had a plane that had already shown it could fulfill the mission, and Boeing, which proposed to build an aircraft significantly different than it had tested and hadn't had a single flight that demonstrated all capabilities like LA had. Proven versus unproven. That's the choice that was present.