“Religious tolerance also helped the Muslim empire expand.”  p461 My World History (Early Ages)

Islam spread by war. For example.  Christianity spread all over the Middle east and North Africa, Iraq, and India in a period of 600 years by evangelism.  Islam spread over the same area in 150 years by war.  No religion spreads that fast by peace.  The evidence demands the conclusion that tolerance was not how the Muslim empire expanded.