No surprise, creating books and courses is cheap and it's a shitty business too much people goes into, selling craps for too high prices.
It's very easy, you just have to trap enough people, especially you're never accountable most of the time and there is always the good excuse "you didn't work hard enough on you own".
I've even seen on linkedin someone selling a course to create an alleged 500kβ¬/y revenue by... selling courses. The "good old" scam of training seminars on how to get rich +/- quick by writing and selling books on... infinite loop.
Finally, even nicely wrapped course could be quite a crap honestly, I've got some from a well known company around Godot (name start with a 'G', end with a 't') and the lessons are not very great, there are multiple errors and it's not an easy step by step process to follow, + was not yet updated to Godot 4 at the time.