Izzet Spellementals relies heavily on ETB triggers from Eddymurk Crab (tapping creatures) and Sunderflock (bouncing your board), so Torpor Orb shuts these off completely and is a high-impact answer to their core payoffs. Surrak, Elusive Hunter is a resilient, uncounterable threat that survives their light interaction (Spell Snare, Get Out) and punishes removal attempts with card draw, which matters since their threats are high-cost and your tempo matters less than just sticking a big body. Shared Roots and Earthbender Ascension don't interact with their game plan and are too slow against a deck that can snowball quickly once its cantrip chain gets going, so they come out in favor of proactive disruption and a hard-to-kill threat.