“If you’re going to go to the Moon, sooner or later you’ve got to go to the Moon.”
Flight Director Glynn Linney, summing up the rationale for the Apollo 8 ‘go’ decision, NASA meetings, 1968. Quoted in the 2019 book Shoot for the Moon.

This was a huge decision, a quantum step from Earth orbit flights. Apollo 8 was the first crewed spacecraft to leave Earth’s gravitational sphere of influence going out into deep space, and the first human spaceflight to reach the Moon. The crew orbited the Moon ten times without landing and then returned to Earth. The three astronauts were the first humans to see and photograph the far side of the Moon and an Earthrise. 240,000 miles outside of Earth orbit. Amazing.
While NASA had carefully planned and prepared for this mission, it was still a massive leap. But some things can’t be done in small incremental steps, sometimes, sooner or later, you have to to the moon.

It’s a great book, outstanding in a crowded field. Shoot for the Moon: How the Moon Landings Taught us the 8 Secrets fo Success, Richard Wiseman, 2019.