What did Hezekiah do to the bronze snake Moses had made?

Answer: Broke it into pieces

Hezekiah broke into pieces the bronze snake Moses had made, as the Israelites had been burning incense to it.

“He removed the high places, shattered the sacred pillars, and cut down the Asherah poles. He also demolished the bronze snake called Nehushtan that Moses had made, for up to that time the Israelites had burned incense to it.”— 2 Kings 18:4 (BSB)