Islam started in 7th century. After it used all knowledge of the Ancient world from conquests lets be it Alexandria to Damascus to India, it was unable to come up with significant development of its own like was European Renaissance and Enlightenment. Christianity went through own splits, but Reformation lasted 150 years and was settled in 1648. This was the last major religious conflict in Christianity on European continent. What Islam lacked was secularization but it actually been rewinding backward. Confrontation with much more advanced civilizations of the West, it responded with more religious zeal.
Left had always love affair with Islam. This is not knew, but can be traced to 1948 when Stalin sided with Palestinians against Israel. Left parties became traditionally antisemitic and supportive Islam. This is also more prevalent when Israel is allied to USA. For European Left this is enough to support Islam regardless of consequences.