Mogg Bomber does not get sacced

[fathom brook]

Both me and my opponent played a creature while he has [[Mogg bomber]] in play, but it doesn't get sacrificed. The wording makes it sound like it is not optional?

[distant spade]

https://scryfall.com/card/sth/91/mogg-bombers

Mogg Bombers <:mana3:292901508771610624><:manar:292901508796645397>

Creature — Goblin
When another creature enters the battlefield, sacrifice Mogg Bombers and it deals 3 damage to target player or planeswalker.
Behind every great mogg bomber is another mogg with a shovel and a basket.
3/4

[fickle garnet]

It isn't optional. Also if its not in play when its trigger resolves it still deals 3 damage