I know this has been discussed a couple times before but assuming that Islam either dies quickly or simply never happens, what religion do the waves of expansion from central Asia eventually convert to? Buddhism had been trending before the push west, Christianity would provide a strong religious authority to any leader who adopted it, and Zoroastrianism (if it isn't destroyed by Christianity) was the oldest and likely most familiar to those in central Asia. Or does no one religion gain the upper hand over the central Asia?