Question

Why did the 2nd great awakening happen

Answer 1

The purpose was to reform America. Nobody went to church anymore and everyone was too busy to concern themselves with it. The awakening focused on emotional nourishment and defying logical thinking. It changed religion, social norms, and was what started the move on women's rights and anti-slavery.

Answer 2

Preachers helped to lead the movement. 
So basically they helped inspire it.