The mass creature stealing elements of Emrakul can decidedly turn the battle in your favor, especially since it's a permanent theft of those creatures since you sacrifice them all if Emrakul leaves the battlefield for any reason
This spell can be especially punishing against multicolored decks with optimized mana bases, as it removes nonbasic lands from play
Certianly one of the slowest combos out there on average but lots of good interactions as the game goes on, very robust despite using a creature (you can go off at instant speed) and flexible in build
Why Bracket 4 Reanimator Is Competitive Reanimator decks are a good way to keep pace in a faster game since you can cheat out big threats early
Cards like Corrupted Conviction always have a home, and I could see a couple of copies slotting in here, used to cash in a chump block or removal target or getting even more milage out of Reflection copies
You can think of it as Event B overriding or rewriting Event A