When I first went over this list, I assumed there was a tutor of some kind and all the singletons were part of a toolbox. As it turns out, the pilot is a strident proponent of the adage variety is the spice of life. There is a single copy of Dark Petition, but that doesn't strike me as enough to affect the list in this way.
Typically that adds too much inconsistency to a deck, but here all the singletons overlap enough in functionality with other cards in the deck that consistency isn't affected by much and you gain the ability to keep your opponents off-balance with a wider variety of threats and answers.
For example, the single copy of Courser of Kruphix overlaps with Kitchen Finks and Eternal Witness as value-generating three-drops, most of which block quite well to boot. Grave Titan and Ob Nixilis Reignited are both solid, high-end threats but require very different answers. And the singletons Maelstrom Pulse, Murderous Cut, and Damnation all contribute to a broad suite of removal that can answer any threat from the opponent.
All of this contributes to a powerful but flexible midrange deck built around the power of Death Cloud. The souped-up sweeper can completely decimate the battlefield on both sides…that is, unless you tip the scales in your direction.
Utopia Sprawl both ramps you into a powerful Death Cloud and lets your remaining lands produce more mana. And of course, the bevy of planeswalkers featured below all stick around to keep generating value…value that is relatively more impactful once both players have sacrificed a healthy portion of their resources.
You have Treetop Village and a pile of discard to help ensure that you recover more quickly than your opponent, the latter pulling double duty in preventing fast combos from running you over before you land the knockout punch.
And should you not draw a Death Cloud, the deck can certainly stand on its own with a classic midrange combination of discard, removal, planeswalkers, and value creatures.