"Why shouldn't truth be stranger than fiction? Fiction, after all, has to make sense"

This quote by Mark Twain is a tip that truth is typically stranger than fiction. Fiction is constrained by the requirement to make good sense, while reality is not. It is typically the case that the fact is more intricate and unforeseeable than what we can think of. Twain is recommending that fact is typically more interesting and amazing than fiction due to the fact that it is not limited by the need to make good sense. He is also recommending that reality is often more powerful than fiction because it is not constrained by the need to be credible. In other words, fact can be more effective and more fascinating than fiction since it is not restricted by the requirement to make sense.