Crassus was not the wealthiest man of the Republic. He wasn't even the wealthiest man of his own lifetime, except perhaps during a brief period between Sulla's proscriptions and Pompey's successful war against Mithridates--by the time of Pompey's eastern expedition he "could have bought and sold Crassus," as I'm told Badian used to say. Compared to Crassus' wealth, Pompey was unbelievably rich--his fortune included the spoils of countless wealthy eastern cities, as well as gifts from them and, at least until the passage of the Eastern Settlement, their tribute. By the time of his death Caesar himself was probably wealthier even than Pompey had been. Crassus' reputation for being the richest man in the world is not mentioned at all by Cicero, Caesar, or Sallust--only later authors like Plutarch claim that he was the wealthiest person of all time.

Crassus' wealth was mostly in land, much of it gotten during the proscriptions--like many, Crassus would include the owners of estates he wanted on the proscription lists, and then absorb their property. Crassus failed to hold a provincial command until his death in Syria, and the value of his estates was quickly eclipsed by the enormous wealth that could be made in provincial extortion