Summary: Why was an unknown man insisting he was Alexander the Great received with distinct deference by Roman officials and Bacchic celebration by hundreds of attendants around A.D. 221? Examining Dio Cassius’s presentation in light of contemporary beliefs, one finds that the enthusiastic reception most probably was due to the conviction that Alexander had actually returned physically immortal and deified, either resurrected or never having died at all. The respectful awe of the officials was also most likely caused by either this belief or by their holding that this was the dead and disembodied hērōs of the famed conqueror.
Frankly I have never understood the argument that it is very hard to conceive the idea that someone, in Judea or in other parts of the world, could be considered "risen" (et similia) by his followers after his death.
The problem with a historical Jesus is surely not his rapid deification post-mortem.
The fact that Simon Magus wanted to usurp the Jesus's legacy is there to witness that even in the Antiquity the people accepted without resistance at all the deification post-mortem.
The problem is the Paul's silence about a historical Jesus, united to the belief in the Jesus's pre-existence. All there.
If Simon claimed that he was Jesus Risen, then he did so in the context of people who already accepted that Jesus was probably risen and could easily materialize himself in a new apparition.
Accordingly, people who already accepted that Jesus did something "of great", comparable to what Alexander did.
The point is that we don't know from Paul what Jesus did "of great".
The only "great" action a hypothetical historical Jesus could do, is to predict the destruction/purification of the temple by divine (and human) violence.
In this I agree with both Secret Alias and Dave Allen.