I think that's imposing motive where there doesn't have to be one.Not likely in this case.
The manner of Jesus' death, as a "rebel" against the Roman State, was a great embarrassment to the early Church, which they did their best to play down. The Cross didn't become the main Christian icon until after the Conversion of Constantine, and it is notorious how the Gospels bend over backwards to whitewash Pilate and put the blame for His death onto the Jews. Had His execution been fictitious, its inventors would almost certainly have Him being stoned to death by Jews, as St Stephen was, rather than crucified by a Roman governor.
If you are pragmatically crafting the religion, then sure that makes sense. But, mistake, hallucination, dreams etc are all means by which people can believe the truth of a matter. Even without such extents, we are pattern seeking creatures who like to look for narratives, misremembering an event is yet another way that no motive can be present.