Say that al-Wahhab either died in infancy or never became interest in theology, and consequently the sect that bears his name never arose. How would this affect the course of Middle Eastern and world history over the past three hundred years?
He was simply the one who bore the torch, which could've been anybody.
A political movement will eventually rise against urban harassments of the interior Arabia and there's no other kind of ideology with stronger grip over a disparate tribal people then one of dogmatic religious nature.
Maybe the desert tribes might have reacted against Ottoman/Hejaz influence by turning Shi'ite -- joining in faith with the various groups who IOTL folllowed that creed along the eastern coasts -- instead?