I did a good job of documenting how to call each function, but they were actually struggling with how dynamic linking worked in C. At the time, I was surprised and questioned their ability to problem solve.

Looking back now, it's common for engineers to jump between skills and work in unfamiliar places. Adding a simple Makefile example would have helped them immensely, and may have helped others as well.

I disagree that it needs to be someone else, but you need some empathy, and the ability to observe your users struggling to understand how to improve your documentation. You can't write it for yourself and expect it to be helpful to everyone.

I doubt this.

Like Eistein said, if you understand something well enough, you will have no problem breaking it down in to simple, easy to digest information.

The idea that someone knows something well enough and therefore not able to write good docs, misses the crux of the problem: The writer here failed to understand his audience.

And when someone is educated to be conscious about their audience, I see no reason why the one knows the system best in any way hindered by his/her knowledge.