He didn't need a teacher, he heard it, saw others use it and knew he too, could use it to his own ends, and then proceded to rape the reward, from people more than willing to be shammed.<quoted text>
01. If some one who is unable to even read and write and has no earthly teacher could "modify" Jewish and Christian religion and pinpoint the mistakes from which they deviated from the true path .it is really strange. And if our prophet could do it, what prevented other people in Makkah doing the same?
02. People might claim any thing they wish, there are 1.5 Billion Muslims in the world who believe in the truth and sincerity of the prophet.
So far no new major religion has come up in world in past 1400 years, let us see how many new religions come in the life left for this earth before the End of Time comes!!
And he didn't pinpoint where they made mistakes, that was his modifications being put in place. New religions are constantly coming up, but there will be less and less of them, over time. Shared knowledge will in time kill out the gods