The way I took "obvious" is that these things are obvious to people who have been dealing with such things for years to the point that they don't realize they aren't obvious to those that haven't.
I've noticed that this is a common thing - it's very rare for someone who has spent years in a particular area to sit down and distill things that have become obvious to them over time in a way that can be taught to newcomers.
I've noticed that this is a common thing - it's very rare for someone who has spent years in a particular area to sit down and distill things that have become obvious to them over time in a way that can be taught to newcomers.