To add to Holmes'reply this seems to be a simple case of self-aggrandisement. Isn't being a cult leader all about making grandiose claims ?
And as has already been shown the Oliver discourse appears to predict an imminent apocalypse, leaving no time for the word to spread to lands unknwon at the time.
To deal with osme of the specific points raised, the claim that the disciples were nearly all executed is a very LATE tradition with no support from even nearly contemporary times (older traditions have most of them surviving).
Roman persecution was sporadic - sometimes severe but frequently non-existent, and it is Roman patronage from the time of Constantine that is responsible for much of the success of Christianity.
The sect was already widespread into gentile lands by the time Jerusalem was destroyed. It is hardly clear that Jerusalem acted as a genuine central authority. The early church seems to have been highly decentralised and this structure may well date back to before the fall of Jerusalem.
So the odds against success are not so bad as it seems. The odds are even better when it is realised that if the sort of claim involved is quite common - it would only take one success to produce a prophecy that *seems* impressive. Without knowing how many fledgeling religions made similar claims and failed we do not have a true picture of the real situation.