Christianity is based on these writings whether a Jesus existed or not. The writings are everything, and Christianity is nothing without them. It's been that way since people at the end of the second century started paying attention to them.
Maybe you would like to do a little more research on the development of Christianity.
First, those writings were based on oral traditions and preaching that was already being done. They may have put pen to paper, but they were only spreading the ideas that were already in existent, and had been created by others. Some of these would go back to Jesus himself. And even if you dismiss Jesus, the information presented in the Epistles and Mark go back further than them.
As for second century Christianity, it was extremely diverse. There were groups who believed there was only one god, two gods, 12 gods, and I believe even 365 gods, and that isn't covering all of the beliefs about numbers of gods. There were those who believed Jesus was fully divine, fully human, fully human and divine, etc. There were those who believed that the OT God, the God of the Hebrews, was an evil God. The diversity of early Christianity is much more diverse than it is now.
Also, there were many different Gospels and other Christian "scripture" being written well into that time and later.
Finally, there would be no need for the Council of Nicea, or any of the other councils if what you're saying is true. Basically, no.