Yeah, it's an intriguing theory, and it would certainly makes for delicious irony. I've seen Richard Carrier debate one of its proponents, on YouTube.

I don't know how you'd distinguish the conspiracy in question from the more evolutionary scenario in which some Jews naturally gravitated to Hellenistic culture after the Jewish-Roman Wars, ingratiating themselves with pagans by watering down their religion, and syncretizing it with pagan themes. How do you distinguish the top-down conspiracy from the obvious need for Jewish self-censorship after the destruction of Jerusalem? Each model might explain the same data, but the non-conspiratorial model seems inherently simpler, which is why most historians would prefer it.

But it's true that we'd need to explain why Christianity appealed to the upper class and not just to the poor. I think that's easily done. Roman religion was spiritually inert compared to the Eastern religions, and the latter filtered into the Mediterranean via the Mystery Religions. Christianity is just the Jewish version of those halfway-house Mystery Religions. So there was an appetite for these spiritual therapies for the same reason that neoliberals today might gravitate towards exotic, New Age practices (as Oprah Winfrey and Gwyneth Paltrow do, for instance). It's a matter of floundering in decadence, and often missing the point of the foreign religions you consume for entertainment. Thus, the rich Romans ignored the satirical point of Christianity, or maybe they agreed with the critique as they saw their empire crumbling around them.