Final answer:
The end of oligarchy in ancient Greece was influenced by the conclusion of the Peloponnesian War, the expansion of Athens' control through the Delian League, and the rise of tyrants in various city-states.
Step-by-step explanation:
The end of oligarchy in ancient Greece can be attributed to several factors. The conclusion of the Peloponnesian War resulted in Sparta establishing oligarchies in previously democratic city-states. Additionally, Athens expanded its control through the Delian League, imposing its own laws and taxes on other poleis. Furthermore, the rise of tyrants in various city-states contributed to the decline of oligarchy.