Conversation so far:
What did Sid Caesar start with?
Sid Caesar's television career began with an appearance on Milton Berle's Texaco Star Theater in the fall of 1948.
Where did Sid Caesar go to start his television career?
After the war, the Caesars moved to Hollywood.
Why couldnt Sid Caesar act as a side kick?
Sid Caesar turned down the lead of The Jolson Story as he did not want to be known as an impersonator, and turned down other offers to play sidekick roles.
What did Sid Caesar learn learn while acting in Hollywood?
That job led to a contract with the William Morris Agency and a nationwide tour.

Question: What did this help him learn
Self-contained rewrite: What did William Morris's nationwide tour help Sid Caesar learn?