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The Flavians
It could be the case that an imperial family named the Flavians who ruled Rome from 69 - 96 C.E., at the time when scholars believe the Gospels were written, created Christianity in order to suppress the rebellion of messianic Judaism that sprang up in Judea in response to Roman expansionism and the subsequent infiltration of Hellenism into their culture. Hellenism came from Greek culture and promoted pantheism and rationalism. Judaism was predicated upon monotheism and faith. Naturally, there was going to be war between these diametrically opposed views.
The Flavian dynasty was made up of 3 Caesars - Vespasian and his two sons Titus and Domitian, along with their adopted historian Flavius Josephus. Vespasian was a Roman general who was ordered by the Emperor Nero to squash the revolt of the Sicarri, a group of militant, messianic Jews who believed a messiah would come and lead them militarily to take back their homeland. Meanwhile, forces loyal to the Flavian family in Rome revolted against the last Julio-Claudian emperor Vitellius and took the capital. When Vespasian returned to Rome, he was proclaimed emperor. Vespasian's son Titus stayed in Judea to finish off the rebellion and the struggle was concluded in 73 C.E. when Flavian commanded Rome conquered Masada. The control of Judea by the Flavians required an alliance between them and two families of Hellenistic Jews - the Herods and Alexanders. These 3 families combined had the money, the military expertise, and the knowledge of Judaic literature necessary to produce a new religion that would be based on a new messiah they would create who espoused pacifist views, rather than militaristic ones. They wanted to supplant Judaism with their own religion, one that would accept Roman rule and importune its followers to "turn the other cheek" and "give to Caesar what is Caesar's".
The Flavians and their employees and supporters seem to have successfully written the Gospels of the New Testament, fabricated Jesus as a mirror image of Titus and his wars against the Sicarri, and portrayed Jesus as the messiah the Jews had been waiting for, only a pacifist one, and as the fulfillment of Jewish prophecy. The Flavians also superseeded the Jewish prophet Moses with their creation of Christ. They used elements from the Old Testament (the Hebrew Bible) and just wrote the New Testament over top it, as if it was a continuation of the story of the Old Testament.
Why would the Flavians go to all this trouble? They weren't creating a religion for themselves. They were creating a religion for the Jews. A new religion that would make the Jews more tame and allow them to be dominated by the Romans. It's the oldest trick in the book, literally. It's called cultural assimilation. If you want to conquer a people, wipe out and transmute their roots, their traditions, their beliefs, their religion, the very foundation of their identity and cause them to adopt a new tradition, the one you want them to, and cause them to become obedient sheep. Not only do they have no choice in the matter because of force, but they lose all choice in the matter when they don't even know there's another choice. If they think the religion you created is their identity, because their original identity was destroyed and assimilated, then you have really won the war, not just physically, but psychically and spiritually.
The Flavians and their servants and loyal subjects may have created Christianity. In doing so, they would have used what had come before for inspiration - the Old Testament, Platonic philosophy, Greek mythology, prophets of old, astrotheology, the wars of the Jews, and any other knowledge and symbolism at their disposal to fool the masses and maintain dominion and control of their empire.