people settle, build up their civilization, develop some 'nice stuff'. then that civilization falls in 1 of 2 ways: 1st way: people want that 'nice stuff', so they come in and take it forcefully 2nd way: people on the inside grow discontent with their cushy lives and revolt, inadvertently destroying their civilization completely then the process repeats
thats where the saying 'weak men create hard times, hard times create strong men' comes from