Socrates was killed because he was perceived to be a threat to the Athenian government. He was accused of corrupting the youth and of not believing in the gods of the state. He was also believed to have corrupted other people, including other philosophers and politicians, which made him dangerous for the state.
Philosopher was also known for his great powers of persuasion. By talking with other people, he could convince them that he should be listened to. His position as a teacher gave him access to political power, which made him more threatening than if he were just some ordinary citizen.
The Athenians were afraid that Socrates would use his power to influence their young citizens into becoming idealistic and disobedient towards their government. This would mean they would have trouble defending themselves against attacks from other countries or other states within Greece or outside of Greece altogether.
So the main reason Socrates’ teachings were viewed as a threat is because they were so contrary to what society expected of its citizens. To many Athenians, philosophy was more important than politics. The people who supported Socrates did so because they believed in his ideas, but there were also those who felt uncomfortable with his questioning and would have preferred it if he would just keep quiet instead of rousing up controversy.
