Why aren't my mobs spawning? [closed]
This is normal behavior. As taken from the Minecraft wiki:
When any of these (hostile) mobs attempt to spawn (whether naturally, through mob spawners, spawn eggs, or commands), they are removed from the game instantaneously. When the difficulty is switched from any other setting to Peaceful, all mobs that are not allowed to spawn on Peaceful are removed from the world. https://minecraft.gamepedia.com/Difficulty#Peaceful
Bolded words in the above quote I added myself.