Why did the roman army destroy jerusalem in 70 ce?

The Jews living there rebelled against their Roman reign. Emperor Nero decided that what they did wasn't okay, and he launched an attack against Jerusalem, the Jews' religious stronghold. 
It turned into a slaughterfest of Legionnaires killing Jews and ransacking the city. This eventually led to the Romans burning down and destroying the Jews' Temple that served as the center of Judaism. 

Yes, reasons why is sectionalism compromise of 1850 and secession i hope this

They were eliminating problems caused by industrialization, urbanization, immigration, and corruption in government