Hey, I've had numerous theists ask me to try and explain why The Bibles stories, written by many different authors from across the globe, fit together so well. I've never had an answer, anyone care to help?
I can think of several things. One, they don't. There are many differences between the various gospels, such as when Jesus was crucified, who was present when he rose, etc.
Second, the various books of the Bible were not written down once, and then locked in stone. They have been altered, updated, changed and rewritten many times over the centuries. It's easy to get a series of stories to sync up to some degree when you can rewrite them to match.
I think they appear to fit together so well because later authors/storytellers could craft their tales from the legends, traditions, and writings that had come before. Also, there were many, many writings that did not become canon, and it was because they "didn't match". Humans created a somewhat cohesive statement about God on purpose.
"Across the globe" is the part of your question I find most interesting. It's actually partly true. But the reason it's true is that the Bible was still being written a millenium and a half after the putative Jesus supposedly lived.
The origins of the Bible are in mythological stories. We have no idea how far back the stories go, but the actual writing was done around 600 BCE. And they never stopped. Even during year 1 or year 30 the Jewish people were still tinkering. So, begin the "Greek Testament," AKA New Testament: the writing didn't happen during the event, any more than the story of Adam and Eve was written during the non-event. Those who wrote had never even met this Jesus person.
And the gospels were written hundreds of miles away and by people who had no direct knowledge of events, assuming there were any. They incorporated the stories of their own pagan gods, elements of astrology, and used some of their own gods as early martyrs so they could keep worshiping them. But wait! That's not all!
They continued to write and edit and change and lose. Of the hundreds of once-extant gospels, few remain. Some of the stories in the Bible don't appear until much later. And the theory developed that later "inspirations" were better than the older stories because they were fresh!
Maybe you should ask them why the Bible stories fit so well with tales from OTHER religions.
Virgin birth, resurrection, floods, specific miracles.. they are nothing new and lifted from other sects in existence for thousands of years before Christianity came about. Even Christian holidays were stolen from pagan celebrations.
The Bible stories are 'somewhat' similar to each other because they were all lifted off of the same poor people they decimated.
I've tried pointing that out, but they will insist that Satan is the "father of lies" and is capable of altering the historical record to make it look like those other religions are older. *eyeroll* Logic just doesn't work on them.