MTG has many ways to donate or make your opponents take control of your cards, and sometimes, your whole deck revolves around your opening to give them a lose condition
So not only is he a strong commander in general, but people may also assume that you're playing a more competitive version of Zur instead of a jankier Cycling deck
Vigilance is missing on purpose because it seemed odd to grant the ability when it already had the ability to untap itself
There are certainly downsides here, most notably that exiling your fallen creatures eats into your reanimation options
Goldspan Dragon generates 2 mana whenever it's targeted, which comes in handy for when playing it on curve and needing a bit of juice to Counterspell some pesky removal
Slash of Light performs well in this playstyle, especially when you want to punish a player before a Crippling Fear resolves