If they control three, their opponents mill eight times as many, and so on
The backside, The Grand Evolution, puts creatures from your graveyard into play, distributes some +1/+1 counters, and lets your creatures fight others for just mana
In green, its easy to play a large number of different, nonoverlapping two-card combos that make infinite mana, for example
Craterhoof Behemoth The best go-wide finisher If you've played against any kind of green go-wide deck in Commander, and especially if you've faced an elves deck, you've probably seen a Craterhoof Behemoth
With a well structured manabase, and some ramp to smooth out fixing, you should be able to cast your cards on curve consistently