I recently read a comment that speculated that Romans, had they not adopted Christianity, would have still eventually become monotheistic. The basis for this was that they saw Sol Invictus as the one main god, with all other gods in the pantheon being manifestations of Sol Invictus.
Is there any truth to this?
Follow up question: Was the 'Sol Invictus' which gained popularity the same religion/deity as Elagabalus, which was pushed by the ill-fated emperor which took the same name? Also, what was the relation between these sun cults and the earlier monotheistic cults, like the cult of Mithras?