Geography. Turkic tribes were converted by the Persian part of the islamic world. In terms of culture and civilization, the Persian world endured in the bosom of the Arab conquests, somewhat comparable to how Rome conquered the Hellenistic world & absorbed its culture. Consider that prior to being absorbed into the islamic world, the Turkic groups lived in tribal (semi)nomadic societies that had little to offer in terms of civilization in light of running an empire. All of this, from higher culture to administrative trappings, the Turkic groups learned from the Persian world. As the Seljuqs burst out from behind the Oxus and into the islamic world, they took that all the way to the gates of Jerusalem & into Anatolia.