The conversation between human and AI assistant.
How were the Jedi forgotten in nineteen years? 19 years is a short time to become a myth between episodes 3 & 4.
Hmm, that makes sense. But why didn't anyone remember them or talk about them?
The Empire was very effective at suppressing dissent and controlling the media. They may have actively suppressed any information about the Jedi or painted them as enemies of the state. With the threat of the Death Star looming and the Empire in control, people may have been too scared to openly talk about the Jedi.