Pg wing tips,
It is off topic, but I'm going to disagree with you.
Originally aircraft such DC3s carried two pilots.
The fact that they were ferried single crew by the ATA during the war proves that the two pilots were not required to operate the aircraft.
You only have to read "Fate is the Hunter" to see that CRM effectively did not exist.
The reason for having the two pilots was to re-assure the travelling public that they were safe in the event of pilot incapacitation, and also because the early aircraft had no autopilots.
The 737 requires two pilots because of certification due to it's size. Other than that any competent B737 pilot could operate one single crew in the same way that a Citation can be operated single crew, if a few adjustments were made to the position of some of the controls to save having to reach across the flight deck.
I'm not saying that it would be as safe as an proper two crew operation, I am just pointing out that CRM and monitoring is not the reason that we have two pilots. CRM came after the requirement to have two pilots and was developed to make them more effective as a team.