Then Arabia could have half cost inquisitor as part of their UP, instead of removing nonstate religion on city acquisition.
One large reason other religions fell out of favor, is because many Islamic nations, such as the Abbasids, allowed other religions to exist in most cases, but put strict limitations on those who practiced other religions than Islam, as well as making them pay higher taxes.
They were called 'People of the Book', which meant they were free to practice their religion. Religions in this exemption where Christianity, Judaism, Sabianism, and Zoroastrianism. But they were not exempt from restrictions on everything from where they could go and what they could do for a living in the extreme end of things. They also had to pay a poll tax known as Jizya, which was sometimes very high in times of need. It seriously went as high as 80% of assets in a few cases.
Due to the tax and restrictions, there was a steady conversion to Islam. Also some people saw Islam as the new true faith due to the Muslim conquests being so spectacular. It really did look like they were being led by God to some people. Later on the pressure of the Islamic culture, and the great gains and science, art, and technology, made Islam look even more attractive.
The conversions happened steadily in some places. Zoroastrianism didn't just collapse when Persia was taken. It just slowly faded out in favor of Islam.
There were of course a few inquisition like activities, but it wasn't the dominant drive behind the growth of Islam.
Right now Leoreth presents this by having the religions simply vanish, when if he were to try and do it historically the religions should slowly fade away. If you truly want to simulate the way Islam spreads early on, then a civic of some sort should be implemented to show the Jizya tax, which would generate extra income per other religions in a city, yet cause unhappiness based on the religion there, while slowly fading out other religions. But that is probably not doable. Even SoI had nothing related to this and just stuck to inquisitions.
Historically for Islam getting rid of other religions with inquisitions simply doesn't fit.