Toxrill as a Commander is extremely telegraphed, and if you run any removal at all , you can kneecap their mana rocks or just remove it when it comes down
The Ozolith is a great artifact that helps to ensure those counters stick around, even if those creatures get removed
It also produces the exact same amount of mana it costs to activate Breya, Etherium Shapers abilities, meaning you can sacrifice three artifacts to play them if your lands are tapped out
Changes in the game can also be seen by comparing new and old cards that share a converted mana cost
Flying, hasty damage is a big deal, especially in a world of planeswalkers (Im looking at you, Gideon, Ally of Zendikar)
It doesn't matter who's responsible for this, and there's no direct benefit to attacking another player's battle