Why was Socrates highly controversial figure?

Socrates (469-399 B.C.), an Athenian philosopher known for his early reflections on ethics and his development of the Socratic method, caused controversy in 4th-century Athens for several reasons. First, as a self-styled "gadfly," Socrates pressed the Athenians in the streets and the marketplace about their basic convictions and assumptions, and questioned much of traditional wisdom, showing that much of popular opinion had no ground or warrant in right reason. Many Athenians were upset by Socrates' close probing and his denial of traditional beliefs especially with respect to the Greek gods. Secondly, Socrates' association early in life with some opponents of Athenian democracy raised controversy and opposition. Thirdly, because he found a large following among the youth, many Athenians thought Socrates was corrupting the next generation of society. On account of these points of controversy, Socrates was charged with impiety (asebia) and corrupting the youth. An Athenian jury convicted him, and he was compelled to drink the hemlock. Socrates' defence of himself against the charges (or rather Plato's construction of it) can be found in the well-known Apology.