Sallust criticized Sulla for his work but on other side he was supporting Caesar who was dictatorial. Sallust
ignored Caesar activities like obtaining extra ordinary command and power using triumvirate program, treating the senate as his creature.
The declination of all the society include roman, Athenian and others were cause of greed for more power and wealth. Once people got wealth and power, they started using them to gain more and that cause corruption and inequality among the citizens. The rule of law and justice is the only solution to avoided corruption.