In 1837 the Eastern USA suffered an economic collapse. Many people lost their jobs, and as Banks went bust they also lost their savings. People were bankrupted and factories and businesses closed.
The Mormons, whose Bank also collapsed ruining many non-believers, became one of the more popular scapegoats for the ruin. This resulted in many Mormons choosing to move West in the face of increasing violence. The increasing population had made land hard to come by.
This combined with the desperation and increasing crime in the East forced people to consider moving West. The Crisis became a big PUSH factor in encouraging people to migrate westward.