Some conquerors are more parasitic than others. The Greeks and Romans brought dynamic cultures that, in the end, tended to elevate many of the peoples they conquered. The Arabs and Turks overran many nations that were more advanced and so ended up becoming more Persian or even Hellenized as time went on - at least outwardly. But Islam’s god is both transcendant and omnipotent and this results in a kind a fatalism that is deadly to temporal developement. If things go wrong it is “god’s will” and what can you do? So things don’t change much and when they do it is usually seen as change for the worse and resisted.
Islam seems to have not moderated barbarian behavior for say the Turks - in fact it justified their way of life - raiding and pillaging - as long as it was against infidels so that culture/people did not change for the better.