Actually if you look into it a little more, and speak with authors today, a lot of authors heavily think about the themes they’re trying to explore in their work and how to best express them. Similarly, sometimes authors aren’t even aware of some things they’re exploring in their work (for example, latent trauma).

Honestly, writing literature is not dissimilar to programming in this way. You have to consider the structure of your piece as you build it, and then even if you do so you might create unintended behaviors.