The concept of resurrection wasn’t even new when Christianity started, it was something that existed in prior religions. Most likely inspired by someone who everyone thought had a mortal wound healed up over a few days merged with the concept of plants growing anew in the spring. Mix it with something like Prometheus being tortured for sharing knowledge and you have the creation and Jesus dying for our sins. The parts are all there from prior to the timeline that Jesus was supposed to have lived.

Like entertainment media, if you look at what came before you can see the inspiration for whatever was the big thing at any point in time. There isn’t really anything new under the sun, just new takes on existing concepts.

Personally I think that someone named Jesus probably did live and inspire people who eventually wrote stories that were inspired by prior religious stories and attributed them to him. He was probably crucified, and the resurrection was likely something that someone a couple hundred years later wrote while inspired by other religious stories.