A 3/3 flyer in Mono-White for three mana is not something you'll normally have as an option
2 Green-Purple Luffy Hitting Fast And Hitting Hard Sets: [EB-02] Anime 25th Collection Before booster set 11 was released, Green-Purple Luffy reigned supreme as the strongest Leader card in the game, and while it may not have that title anymore, it's still very powerful
Even if an opponent has removal to take care of the Idol, it will leave behind a similarly sizable token that also has trample unless it's exiled
Automaton can also benefit decks that arent tribal themed, like strengthening Talrand, Sky Summoners Drake tokens
Blightsteel Colossus is twice as hard to remove with its ability to shuffle back into your library if it would enter the graveyard from anywhere
Karlach fits neatly into a red/green ramp deck, making Hardy Outlander a great choice