What are the reasons for Babbitt's rebellion in Sinclair Lewis's Babbitt?

Basically, George Babbitt experiences what many people
still experience today: a mid-life crisis. In his case, it is sparked by the
imprisonment of his best friend. After Paul goes to jail, Babbitt begins his rebellion.
He goes to the movies when he should be at work, he flirts with women (and eventually
has an affair), and goes against the conservative principles of the other businessmen in
his social circle.

However, while Paul going to jail may be
the straw that broke the camel's back, Babbitt was not really happy in his life before
that. He is unfullfilled, as shown in the dinner party scene where he can't wait for his
guests to leave. His marriage brings him no contentment either. All of these are reasons
for his rebellion against the rules by which he has lived his
life.