Well they wanted it that way - being able to independently navigate (if necessary) without benefit of comms with ground control was one of those things set in stone early on. One of the practical reasons were fears that the Soviet Union might try to hack the radio frequencies used to send and receive data back and forth from the earth to moon.
Buzz Aldrin on the first attempt wasn’t simple luck of the draw, he wrote his doctoral dissertation on lunar orbit rendezvous, if something went wrong, Buzz will get you home with a #2 Ticonderoga and some scrap paper.
Outstanding! Didn’t know the Soviet end of it, but I do remember that the Soviets did congratulate us some point right around the Apollo 11 launch...classy of them, considering how hard each side tried.