In writing, everything has a reason. This is nothing new, both in the grand scheme of things and in the realm of this blog. But still, I find it bears a reprisal. And along with it, the idea that that's not always possible.
We readily accept that characters have a life of their own, a mind of their own, and motives of their own. Fictional though they are, real characters are fully-fledged human beings. Well, real people don't always have a reason for the things they do. Sometimes they act on impulse, only later trying to find the reason for their actions.
Arguably, writing is not real life. It is an idealized form of real life, meant to be a medium by which we can tell a story or concept. In that case, we may demand writing to be above the irrationality of humanity. But frankly, I don't think I buy it. We are humans and we respond to humans. When we create, we create humans.
Although we always want to know the answer, the reasoning, the rationale behind people's actions, sometimes the only answer is that they don't, themselves, know.