The early church was persecuted mightily, and yet it grew so rapidly it practically took over the world within a few centuries of its birth. How did this happen? Why did this happen? Obviously, we can point to the sovereignty of God, and that is important to keep in view. But there is another reason why Christianity spread so rapidly: Christianity was (and is -- or at least should be) simple.
It was monotheistic, believing in only one God. This was attractive to those confused by the complex constellation of Greek and Roman gods. To think that there was only one Lord, one faith and one baptism -- that was appealing to them. There weren't hundreds of rules or dozens of rituals to keep straight. Love God. Love people. Trust Jesus. These are simple things.
They're not easy things, but they're simple. There is an elegant simplicity to the gospel, an elegant simplicity that gets buried and lost under a lot of man-made rules. Don't drink or swear or watch movies or dance or wear a two-piece bathing suit or smoke a cigar or listen to certain kinds of music. Only go to these kinds of churches where they read these kinds of Bibles and pray these kinds of prayers. Avoid those kinds of people who frequent those kinds of places.
We add to the gospel (which necessarily takes away from Jesus), and then we wonder why we're not growing the way the early church did! We've lost the simplicity. We've added too many layers of unnecessary things. We've elevated our traditions and customs and demoted the finished work of Christ to something that plays a part in our salvation when it is combined with our ability to keep the rules.
What must I do to be saved?
How did the early church answer that?
They said, "Stop going the way you're going. Turn around and go all in with Jesus. Trust him for everything, and let him teach you how to live."