Many of us here don't intend to affirm Jesus' existence as irrefutable historical fact. We just want to affirm that historically, it is impossible to prove he didn't exist.Jesus doesn't have to be the product of a conspiracy to be unhistorical.
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Because, the number of conspirators and rebels crucified by Roman authorities was so high in that period.
Besides, analyzing the political context, it was very common that a heroic insurgent (a slave, also) who was martyred by the Romans , was heroized and divinized, after his death.
This is a typical Hellenistic attitude: to adore martyrs as gods and to start inventing extraordinary stories about them (like miracles, divination, etc). Not to mention that the anti-Roman sentiment was very high among Greeks, so they praised whoever stood against the Empire.
That's why Christianity at first was more a political. social movement than a religious one.
Even Eunus, the rebellious slave protagonist of the first servile war, was considered a great psychic...endowed with magical powers. This doesn't exclude his existence.