There have been numerous heresies since the time of Jesus of Nazareth, including those contemporaneous to His life on Earth. Pilate, the Roman governor who allowed His crucifixion, agreed to a conspiracy that allowed the Roman guards to claim his body was stolen. That way they wouldn't have to confront the observable (by scores of witnesses who never denied what they had seen despite pain of death) that He had, indeed, risen.
In the ensuing 2,000 years, there have been denials of His divinity, the most famous being the Gnostic gospels; there have been denials of His existence, despite the record of the historian, Josephus. Again, many witnesses who might have enjoyed a much easier, not to mention longer life, had they simply denied the Christ, testified to what they had seen and heard.
The late Charles Colson wrote about why Watergate proved the resurrection. He said the men around Richard Nixon were men of power, yet they couldn't hold together a conspiracy for very long.