Legendary creatures you control get +2/+2
There are lots of situations where you draw it and don't want to use it at first, perhaps you have lots of lands or only very low costing cards, the Chrome Mox will sit in your hand but instead of being dead it will be a get out of jail free card
Not only is this Maui a 7/5, but it has the evasive keyword, helping you knock out your opponents evasive characters with a single strike and making it incredibly resilient to attacks
Basically, the deck feels unbalanced, and if players know your strategy is basically to go all in on creatures, they're going to be far more aware of your combos and keen to stop them
You can open Phyrexian Urabrask in Set, Draft, and Collector Boosters, in both non-foil and traditional foil