Answer: The word alienate as used in paragraph 23 most likely means to separate or to undermine their previous positions of power.
Explanation: The definition of alienate is to cause to be estranged or to make hostile, typically where a form of attachment previously existed. In this scenario, it's implying that the "wealthy and rich" were previously supportive of the individuals that were opponents to Caesar. It can be inferred that these individuals no longer hold the power they previously held by being supportive of previous rulers.