Most tutorial writers are not aware of how to create educational materials. They don't think deeply about the learning objectives (what the reader should be able to do or understand at the end), don't understand how to provide concise working examples, how to "scaffold" learning, and so on. It's often just a dump of the things they learned and maybe how they learned it, but that doesn't mean it'll work for anyone else.

Creating teaching materials (tutorials, documentation, etc.) is hard, and few tutorial writers are getting feedback from actual students/readers. If you're never watched how novices work (and struggle!) with the materials that you've created, you don't really know what's missing or confusing or overwhelming. Even though I've been creating training courses for a long time, I still never know whether I'm making too many assumptions about what the student knows -- this is the "curse of expertise" -- and where they'll get stuck or lost.

(btw, I talk about some of the theory of learning with examples in my "Human Learning" presentation that you can find on YouTube: https://www.youtube.com/playlist?list=PLBHctPrH7Z2-BcpRWJ0uF...)