Well, yes, it’s a coincidence but not a very surprising one. If you were to write a novel that has a pope as a character, probably you’d choose from one of the historical names.
During the last hundred years we have seen these papal names:
John Paul
John
Paul
Pius
Benedict
We can go back a bit further and find Leo and Gregory.
It seems to me that, of all these names, Benedict is the one most likely to be chosen by a novelist: It’s a “regular” name (I’ve met lots of guys named Benedict [even if they go by Ben] but never a guy named Pius, and I’ve known only a couple of Leos) but hasn’t been used by a pope too recently (Benedict XV died in 1922).
Of course, Gregory is an even more common name–and John and Paul more common still. Precisely because of how common those names are, I think a novelist would go with Benedict: a good balance between too-common and too-old-fashioned-sounding.