They could get to know each other without supervision.
and
They had a cheap fast mode of transportation to go to places and to get to school, home and work without the expense of a car.
Civil wars. Probably the most important single cause of Byzantium's collapse was its recurrent debilitating civil wars. Three of the worst periods of civil war and internal infighting took place during Byzantium's decline.
Carlolingian empire I hope this helps
Either 9 or 5 sorry if I’m wrong