"For want of" is a preposition meaning "because of the absence of"

https://en.m.wiktionary.org/wiki/for_want_of#English

“for want of” in this context means “because of not having” or “for lack of”

It’s an older way of writing English. But not like super old. Basically the kingdom was lost because of 1 missing nail.

It’s so contrived and yet needs so many leaps of abstraction that I don’t think it makes its point well at all. “Bro my controller totally didn’t work that time! We would’ve won the match otherwise I promise.” Do you really think it was the controller that lost the match?

It is a well-known proverb that is centuries old [1]: it's essentially a canonical way of refering to the concept of something small having big consequences.

Proverbs are often contrived (e.g., "Those who live in glass houses should not throw stones" - who lives in a glass house?).

[1]: https://en.wikipedia.org/wiki/For_Want_of_a_Nail

I hate everything about this, thank you for sharing the context

They're talking about a horseshoe on a horse which was being used to deliver an important message

There are too many leaps of abstraction, which to me, proves the missing horseshoe nail is irrelevant in the big picture. Too many other things could have transpired positively for the kingdom in a space so expansive. It’s classic scapegoating. “Bro my controller totally didn’t work that time! We would’ve won the match otherwise I promise.”

It's an ancient proverb demonstrating early understanding of complex systems. Not an in depth philosophical argument.

However there are plenty of real life examples of a single small detail causing outsize impact. See: https://en.wikipedia.org/wiki/Alaska_Airlines_Flight_261

It's kind of absurd to think otherwise.

Tbh it seems entirely plausible to me that a messenger being unable to deliver an important message could have an outsized effect on that outcome of a battle. What if they're letting their side know about a surprise attack?

Seems also plausible that risks might apply to the messenger that wouldn’t apply to the troops in garrison—that is, the thousands of other horseshoe nails in inventory could have gone unmissed or doomed a less important horse.

A more robust treatment of risk factors in both ideas.

You want to ask whether the system needs to be tracking nail quality if the kingdom relies on nails that much. You also want to be asking why critical information is being sent by only one messenger.