You show yourself to be quite ignorant of history. For the first 300 years of its existence, Christianity was outlawed. Despite this, and despite its leaders and followers being executed on a regular basis, it managed to spread all over the Roman Empire, and as far east as India.
And the Christian sects that deny the bodily resurrection are just that: sects. The resurrection is the lynchpin of the Christian faith; without it, Jesus is just another philosopher.