Most HNers, and sadly I include myself in this, couldn't fight their way out of a paper bag. We read Sun Tzu because it is recommended reading in the intelligentsia's mindset. It seems cool to learn battle technique from an ancient Chinese text. If I wanted to learn how to really fight a battle I'd go to Sandhurst or West Point.
Origins according to a many-times-over gilded comment on reddit (I forget which sub) went something like this -
subservient office culture in Japan where the big boss was reading it, so it spread to the entire organisation from where it spread to other organisations. It got to a point where no one knew why they were reading it, just that they had to. Around the same time it caught imagination of the Americans because of the Japanese (who were actually pretty efficient at their jobs).
Will look for the comment and post if it takes me less than 15 mins.
Edit: forgot how bad reddit search was. While I did not find what I was looking for, this [0] is one high quality answer you may be interested in. Only top comments are heavily moderated on that sub.
