Why would philosophers like Socrates start questioning traditional beliefs?

Socrates tried to get the brightest youth in Athens to start thinking for themselves and question commonly held views. It was not popular with the influential classes as it undermined their grip on people, and they set out not to counter him with reasoned argument, but destroy him.

Rather like today, when those with vested interests label those who question extreme climate change as 'deniers' and try to damage them.