Tacitus says:
But all human efforts, all the lavish gifts of the emperor, and the propitiations of the gods, did not banish the sinister belief that the conflagration was the result of an order. Consequently, to get rid of the report, Nero fastened the guilt and inflicted the most exquisite tortures on a class hated for their abominations, called Christians by the populace. Christus, from whom the name had its origin, suffered the extreme penalty during the reign of Tiberius at the hands of one of our procurators, Pontius Pilatus, and a most mischievous superstition, thus checked for the moment, again broke out not only in Judaea, the first source of the evil, but even in Rome, where all things hideous and shameful from every part of the world find their centre and become popular.
That's pretty straight historical reporting. Jesus was executed on the order of Pilate. It's also a historical fact that his disciples very quickly started to spread the news that jesus was alive. Why would they do this? Why couldn't either the Roman empire or the Jewish authorities end the rumour by producing Jesus' corpse?
If Jesus didn't rise again there must have been a conspiracy. Who could have been behind it?
I've yet to come across a satisfactory explanation other than that Jesus rose again.