Among other reasons, Rome was destroyed by admitting so many people who had no loyalty to Rome.
One of the Other reasons is "Democracy", whereby the power blocs in Rome granted the vote to all these unloyal "citizens" and then bribed them with bread and circuses to support the existing power blocs, very much in the manner that Democrats bribe poor people with welfare to keep voting Democrat.
The Democrat policies of unlimited "immigration" and Welfare vote bribing are exactly what destroyed Rome.