The man painted grenades to look like easter eggs and pinned them to the sidewalk. Dumb people ran to pull them from the nails, cooking them, which then blew up and kill them.

I think it would explode before they cooked it

why does picking up an easter egg make you dumb?

Because a smart person would be able to see that the pin is nailed to the ground and therefore deduce that pulling the grenade away from it would cause the pin to be pulled resulting in an explosion.