[elric]

If you thought the Butlerian Jihad was silly, you may have missed a few important nuances in Dune. I mean I suspect the concept was originally a convenient way to explain why tech in Dune hadn't advanced all that much in 20k years, but the in-universe explanations are pretty good.

In fact they are somewhat similar to the reasons why the Melnibonéan empire fell in the Michael Moorcock Elric universe: people got lazy, spent their time drugged out of their minds, and cruelty seemed to be one of the few things to get a rise out of them. In Dune labour was delegated to (thinking) machines, in Elric it was delegated to slaves. Eventually such a society will collapse or be conquered.