Hell yeah I've read those books, they were fucking gold!
Also ATTENTION EVERYONE: GREAT EXPECTATIONS IS SHIT>>1329
It's because the civilizations forget what made them great, and start taking their greatness for granted, so they start assuming everyone can be great and cancer people who kill great societies and create shit ones are worth listening to when they say "Your society should change to make me happier".
Multiculti societies fail. Either the foreign influence spreads to make a group have less in common, or the foreign influence solidifies in a little cliquish circle of foreignfaggotry.