Conversation so far:
what did Ozzie Nelson do on the radio?
Besides band appearances, he and Harriet had been regulars on Red Skelton's radio show.
did they have any top hits?
The Adventures of Ozzie and Harriet.
The show went on the air in 1944.
how long was it on the air?
until 1949.

Question: why did it end?
Self-contained rewrite: why did The Adventures of Ozzie and Harriet end?