Creeper explodes without Human Interaction

This is not a mistake, but the mechanic of Creeper, he attacks any mob that inflicted damage on him, apparently the witch was standing close to the golem.

Generally, Mojang tries to have no damage done to the world that the player is not causing or able to stop themselves. So a Creeper should only ever explode as aggro to players. No other mobs.

I believe this behavior is intentional judging by the resolution of MC-74908.

Witches only attack if there's a player nearby. If the witch then accidentally hits the creeper instead of the player, it's still "technically the player's fault" for provoking the witch.