Specifically Christ was such an overwhelming mover that the fact that paganism would still be the course had He not lived,
While I don't feel this begins to approach proof, I would agree that perhaps the best argument for Jesus is that we're still talking about him widely and earnestly 2,000 years later. Can't say that about very many people.
It seems constructive to try to understand his staying power, and this is aided by sidestepping the distracting "Is Jesus God?" question. My pet theory goes as follows...
A central fact of the human condition is that we experience reality as being divided between "me" and "everything else". This perception can reasonably be proposed as the source of the majority of our personal and social problems. So, a rather big deal, that affects all of us.
Imho, the genius of Jesus's teachings are that they addresses this core problem directly, AND
in a way that is very accessible to the average human being. "Love your neighbor as yourself" is both very practical AND very simple advice for easing the personal and social pain arising from the "me" vs. "everything else" perception.
This example also serves we wannabe philosophers, in that it demonstrates that quality philosophy is both 1) well connected to the facts of reality, and 2) is well packaged in a straightforward language that is easily consumed by readers.
Fancy arguments designed primarily to inflate the ego and social position of the arguer fail this test. What is the point of brilliance if few of our fellow humans understand WTF we're talking about?
These days it's become popular to endlessly analyze our own personal psychology, the navel gazing enterprise. The problem with this approach is that one analysis leads to the next, to the next, to the next, in an endless loop, and the process serves mostly to reinforce the core problem, the perceived division between "me" and "everything else".
Jesus is brilliant in blowing right on by this huge pile of unnecessary work. I hear him saying, "Forget all that, forget you, go help the guy in the soup kitchen." In other words, change the @#$% subject. Billions of people have tested this advice and found it works, thus the fellow is still popular.