What's a post here that didn't make much of an impression on you at the time, but that inspired significant changes the more you thought about it later?

u/Different_Wealth8143 Made a post ["Mines aren't infinite"](https://old.reddit.com/r/worldbuilding/comments/1wgq76t/mines_arent_infinite/) a few weeks back, and they mentioned in their (ultimately top-voted) comment to their main post that aluminum could be more useful to a fantasy world than a lot of people realize (if wizards can use their magic to accomplish things like electrolysis that in the real world, without magic, couldn't be done at large scale until the 1880s).

I'd recently become obsessed with aluminum in my own fantasy projects, and I quickly jumped in with a link to my own recent post about how aluminum bronze would also be more useful than pure aluminum — except that my caveat "if the easiest copper deposits haven't been depleted yet" was doing a lot more work than I'd recognized.

It turns out that by jumping too quickly into their smaller specific comment, I'd actually missed the core point of their main post: In both of the projects I'm primarily working on (one primarily Medieval, the other primarily Enlightenment), the most convenient copper deposits would logically have long since been depleted.

Once I started taking the main point more seriously, I realized that the faction I'd envisioned as becoming The Aluminum Bronze Faction™ would have to settle primarily for pure aluminum after all because there wouldn't be enough copper left for them to turn most of it into bronze.

Has anything like this happened to anybody else? What was your inspiration that took you awhile to catch up with?