These JS "lessons" just tell me what to do but don't explain why or how it works

FYI, you’re not the only one who’s noticed this issue. You can review this post for eg where I made similar comments What is the point of 'Learn Functional Programming by Building a Spreadsheet'? Seriousy? - #15 by hbar1st

If you look at the responses, it will give you an idea of how hard it is to address this issue.