Adullah M
It was the nature of the olden Emperors or Kings that when they build the new Capital City then would destroy the Capital Cities of those old rivals. This assumption was hold true with King Sennacherib of Assyrian Empire , build by his father Sargon II who was killed in the battle. King Sennacherib build a new Capital city in Ninnava with a very beautiful Palace , then decide to send army to destroy Babylon .
John
That Assyrian King had nothing better to do, that day. Alexander the Great (Alexander of Macedon) burned down the Capitol of Persia after partying in it. I forgot how to spell the name, something like Percepis. Julius Caesar wept when he saw a Statue of Alexander in Spain.
Anonymous
Because he hated the English and thought Babylon meant Baby London.