The people expecting Xenagos to stay at $40 were betting on a two-color planeswalker being so good that it would see play as a four-of in multiple tier 1 decks, which never seemed likely to me
It's a fantastic way to close out the game in EDH, too, jumping your whole team, repeatedly if need be
It doesn't have to be your own character, either
The deck features 3 copies of Yorvo, Lord of Garenbrig, which is already a very strong creature at 4/4 for 3 mana, but also gets stronger each time you cast a green creature (and all your creatures are green!) The deck adds 3 copies of Thunderous snapper, which is already a 4/4 for 4 mana, but also draws you cards each time you cast big creatures
Wheel of Fortune has the advantage of filling your graveyard and enabling discard payoffs, while Timetwister nerfs graveyards