Apollo 10 was practically a full dress rehearsal of moon landing, except the landing act. As such, its crew (astronauts) gained all the experience needed for a moon mission. They were best suited to "expect the unexpected". Despite this, why was a completely new (an "inexperienced" crew, w.r.t Moon mission) selected for Apollo 11? (unless of course the answer is "it was planned earlier"). Would it not have been more risky to send the "first timers" as compared to the crew of Apollo 10?
The question is specifically about repeating the crew of Apollo 10, on Apollo 11 - which was the first human stepping on moon - that too American. Possibility of another failure like vanguard launch would have been greatly reduced.