MCarney said:CBS didn't cancel "Leave it to Beaver" - the sponsor (Ralston Purina) had a deal with ABC and moved the show there.
IIRC from what I've read, "Beaver"'s original sponsor was Remington Rand, and the show wasn't helping the sales
of their products (typewriters, electric razors, etc.). The rest of what you say is, to my knowledge, correct;
Ralston Purina made a good move in putting "Beaver" on ABC, which was more comfortable with kid-oriented sitcoms
than CBS was ("Dennis The Menace" notwithstanding).