Thomas Hobbes
Leviathan

Believers would argue that its victory is because of the underlying truth of the narrative. Skeptics might assert that its power is because of the zeal with which its adherents persecuted and stamped out completing and threatening religions.
However, number of adherents cannot necessarily equal truth, because these numbers vary over time. And intolerance cannot be the deciding factor, because these particular religions are not unique in their persecution of other beliefs. Furthermore, Christianity was in no position to persecute for the first formative centuries of its existence.
What do you suppose it is about monotheism that enough of our ancestors found compelling?
(This posting was contributed by Dane, and incorporates a few minor changes from me)