The announcement explained that while they initially planned other bans, internal testing showed that banning maindeck cards had minimal impact on win rate or play patterns, regardless of how strong those cards appeared
Zimone naturally gains more +1/+1 counters over the course of a game if youre casting X-spells, and each turn, your spells get cheaper
It also has the same edge case as Fanatical Firebrand: if you need just a little more damage to win, this is a winning top deck
We dont get to filter our mana to cast the spells we exile if theyre a greater mana value than our artifact count, but the Treasure generation certainly helps us get there
Devotion decks are notorious for generating a frankly ridiculous amount of mana, so anything you can sink your mana into is an extremely attractive inclusion
Combining these numbers with your average win attempt turn can give a really strong indication as to where your Commander deck stands