Why did early attempts at sleep teaching fail? How did they improve it?

The most logical reason as to why sleep teaching failed is because they didn't consider the strength of a child's mind. They wanted to show the kids sane reality, which was really overpowering and incomprehensible. In fact, they even changed strategies years after the fact, moral instruction turned into the favored lesson. This was accepted to be suitable on the grounds that it was not rational idea.