I think we can agree the parents were sorely ignorant in the treatment of their children. And I wouldn’t rule out the influential potential of the book. It’s a different matter, however, to state the book was definitively the catalyst for the unfortunate, tragic outcomes that befell the families.
As a child I saw a cartoon that was made during WWII. Today this cartoon would not be PC.
In the cartoon a “Rosie the Riveter” type woman goes off to work and leaves JR with a sitter. Before she goes she leaves a book Called “Child Psychology” with the sitter saying “Use this it helps me”. Well you can guess JR is a brat! The sitter reads the book and does every thing it says and nothing. Finally when “Rosie” comes home the sitter tell her “we used the book but it did not help” to which “Rosie” says “Strange it always works well for me!” as she is putting JR across her knee and beating his a$$ with the book.