"Corruption" has a relative meaning. As Philipvs told, what was considered inadmissable in a Republic such as Rome was perfectly tolerable in the elites of powerful monarchical states. Later powerful Roman magnates were simply doing what powerful figures, pretenders and rulers always did in Hellenistic monarchies, the most glaring part being the sponsorship of private and civil strife vying for power. What gives them a corrupt image is the fact that the Republic rested on a solid basis of laws and aristocratic codes that officially condemned this, and not merely on the power and influence of the sovereign.