Why do you think the growth of the territory of Rome in 2-1 centuries BC was accompanied by civil wars?

Civil wars accompanied the development of the Roman Empire throughout. The annexation of new lands and the competition for the right to rule the new lands and metropolis were very often the reasons. The elimination of local government caused discontent. The conquered peoples rebelled many times. Example: Battle of Thessalonica.
Despite the fact that the Romans considered themselves a model for the development of society, they were far behind Greek society. This was not in favor of the Roman government. The cruel treatment of slaves in the Apennine Peninsula itself (metropolis) has caused frequent slave uprisings.