Ask HN: Why do tutorial writers combine 10 technologies when 1 or 2 would do?

Suppose I want to learn graphQL - most of the tutorials are a combination of express, react and 20 other things, when most of these aren't going to help me learn what I originally came to learn. I saw a course on blockchain which explicitly stated it is for beginners ("no coding experience necessary") and they picked JS along with 5 other JS frameworks to build a simple toy blockchain when Python would have been a much simpler choice (most of the students were struggling to understand JS Promises and unable to complete the exercises).

Isn't this crazy? I can understand paid courses doing this - maybe they think they're providing more value for the money by tacking as many tech as possible, but free resources? Even they do the same!