co-evolved. I understand that Christianity became big in Europe only centuries after Christ. And that it has changed and fluctuated a lot in its history. But I think there was never a discontinuity of the sort we see since ~2 generations.
"20 centuries" came into play when I deplored a modern fashion in which we're supposed to take the vastness of 2 millennia of highly complex history involving millions or billions of people, strip it from all context, compress it to a few soundbite sized low points and say: "this is Christianity".
-> About continuity and pre-Christian paganism: one of the things that fascinates me endlessly about the christian traditions of my community, is how many aspects of it are obviously echoes of pagan times. Many saints that used to be popular here, are not historical figures but thinly disguised pagan deities. A nearby community has (= used to have) a big tradition of Marian worship, which is almost certainly a continuation of an older cult devoted to a pagan fertility goddess. A nearby Christian chapel built next to a well, located beautifully in a forest in the middle of nowhere, was a place of worship in pagan times. Lots of Roman coins were found around the chapel. People used to walk there and tie strips of clothing from sick relatives to the chapel door. I can go on like this for quite a while. I would argue that the transition to christianity, despite its implicit intolerance at the time, does not seem abrupt but rather "organic".
Same for theology. (Btw, with some exceptions, this topic doesn't interest me much personally. Just like I don't care much for all the pseudoscience in secular academia.) But anyways, a lot of christian theology is obviously classical philosophy in a Christian jacket, with influences from Platonism to stoicism. In fact, christianity did something antiquity failed to do: in antiquity, becoming literate and trained in classical philosophy was very much a "1 percenter" thing. Early christianity brought a "pop version" of this literacy to a much broader public.
To conclude, I'd predict the exact opposite of what you said. To me, the current secular world actually seems more likely to destroy traces of what came before. Turning a church into a hipster lounge is so much more drastic than turning a pagan shrine into a church, or a church into a mosque. The French revolution or the various socialist regimes didn't seek to adapt, echo, continue, soften, change, transform, absorb or even abuse Christianity. They aimed to root it out.
The sudden and rapid abandoning of all things Christian suggests the secular revolution is finally succeeding in Europe. It's Brumaire of Year I. Or rather, Germinal of Year L.
Obviously, in all our secular glory and freed from the irrational, time consuming habits of our grandparents, Europe may never know wars or bigotry or superstition or pseudoscience or corruption again. And this time I will leave the sarcastic quip in :-)