WordPress is very… utilitarian I suppose. People tend to use and know as much as they need to get things done. Curiously that tends to exclude the low level core load process.
It doesn’t help the situation that (unlike modern frameworks) WordPress doesn’t use a complete routing logic for everything. Front-end is governed by rewrite/permalinks, while back end is a spaghetti of different non-virtual endpoints.
The closest I had come to mapping it out myself is my core load graphic.
But overall there are so many things going on, that summarizing it completely is rather futile. You just live and learn (if you choose to :).