Conversation so far:
How many people were in the group Belmont?
Three with a later addition of Dion.
Why did Dion DiMucci and Belmont break up?
There were musical, personal and financial differences between Dion and members of the Belmonts, and in October 1960, Dion decided to quit for a solo career.
Did Belmont continue producing music after Dion DiMucci's departure?
After leaving Laurie Records The Belmonts continued to record throughout the 1960s on the Sabina, United Artists and Dot labels.
Was I Wonder Why a success?
It was the group's first national pop chart hit, in 1958.

Question: Was  I wonder why  the only success of the Belmonts?
Self-contained rewrite: Was I Wonder Why the only success of the Belmonts?