In many ways, both men were trying to be a part of both worlds. Pompey was a pleb fighting for the aristocracy, and Caesar was an aristocrat fighting for the plebs. Despite their different origins, both of these men tried to straddle the growing gap between the two classes. And they both used the same strategies to get what they wanted: appeasing the populace with presents while intimidating the aristocracy with soldiers.
Recognizing this kinship, Caesar formed an unofficial alliance with Pompey by marrying his daughter, Julia, to the aging general. With this marriage, Caesar elevated Pompey to the senatorial class and cemented their alliance.
Caesar persuaded Pompey to include a senator named Crassus into their scheming. Crassus had earned some fame putting down the slave rebellion led by Spartacus, but his most notable achievement was that he was the richest man in Rome, perhaps the richest man in all of human history. These three came together to form the First Triumvirate: an alliance between Julius Caesar, Pompey Magnus, and Marcus Licinius Crassus."