Why did the Optimates oppose Pompey after his return from the East?

Upon his return from the East in 62 BCE, Pompey the Great found himself increasingly opposed by the Optimates, the conservative inner ring of the Roman Senate. Despite Pompey’s desire to be recognized as the state's "first citizen," the nobles grew suspicious of his immense power and prestige.1

The opposition was driven by several key factors:

• Legislative Obstruction: The nobles, led by figures such as Marcus Porcius Cato the Younger and Lucius Licinius Lucullus, were determined to block the en bloc ratification of Pompey’s eastern settlement, which had reorganized the region and established a new frontier system.1
• Veterans' Land: The Optimates refused to grant Pompey’s demand for land to settle his discharged veterans, a move that alienated his soldiers and forced him to seek political alliances elsewhere.1
• Closing Ranks: The nobility viewed Pompey as a threat to their traditional dominance. When Pompey attempted to align himself with the senatorial party through marriage, his offer was rebuffed, signaling that the nobles were actively closing their ranks against him.1

These tensions eventually pushed Pompey into the unofficial political coalition known as the First Triumvirate with Julius Caesar and Marcus Licinius Crassus, as he sought the necessary support to secure his goals.23