Temur Battle Rage nicely illustrates why. With the perfect hand, we now have a Turn 3 kill in Standard Pauper, assuming your opponent doesn't interact with you during those three turns.
Turn 1: cast Akroan Crusader.
Turn 2: cast Rouse the Mob targeting the Crusader; cast Titan's Strength, again targeting the Crusader. This buffs the Crusader up to 6 power and creates 2 1/1 tokens with Haste. They deal 8 damage total.
Turn 3: cast Titan's Strength, targeting the Crusader; cast Temur Battle Rage, targeting the Crusader. This buffs the Crusader up to 4 power and creates 2 more 1/1 tokens with Haste. With the tokens from the previous round, they deal 12 damage total (4 first strike, 4 regular strike, 4 total from the tokens). For those playing along at home, 12 + 8 = 20, or the starting Life total of your opponent.
The same trick also works with Satyr Hoplite. But in this case, it's a 3/3 before buffs on Turn 2, and a 5/5 before buffs on Turn 3. You still deal 8 damage on Turn 2, but on Turn 3 you now deal a whopping 16 damage, bringing your total up to 24 damage.
Granted, either way this takes the perfect hand. You have to draw two copies of Titan's Strength, a copy each of Rouse the Mob and Temur Battle Rage, and three Lands, all of which must come into play untapped and two of which must be Mountains. You also need the Akroan Crusader or Satyr Hoplite in your opening hand, and for your opponent to be unable to interact with you during those three turns. You also get two Scry activations from Titan's Strength, for whatever that's worth.
Unlikely, yes. But certainly not outside the realm of possibility. And even with a slightly less ideal hand, a Turn 4 or 5 kill is even easier, particularly if you can pull off multiple buffs before casting Temur Battle Rage.
I suspect that this card alone will cause more rage than any other in the Standard Pauper cardpool once Fate Reforged is released.