It was not proven that Enoch killed the Sacred Python in Things Fall Apart nor were his reasons given. His father was the leader of the snake cult, so Enoch may have killed the snake to defy his father.
Okoli killed the sacred python in Mbanta.
Enoch was a bold Christian who challenged the tribe on their traditions. His father was the leader of the snake cult, and it was rumored that Enoch killed and ate the python, getting cursed and disowned by his father. Enoch kills an egwugwu, sparking off tensions between the tribe and the Christians.
Enoch did not say anything specific, but indicated that he thought that the gods of his fathers were a sham compared to the Christian gods and system.
Enoch's unmasking of the egwugwu enrages the clan, and forces them into option.
Enoch, a Christian convert, unmasks an egwugwu, killing it.
Enoch is disappointed because he wants the Christians to fight against the rest of the tribe in a holy war. However, the Christian elders realized the wisdom in not fighting such a battle with inferior numbers.