In an SP hybridized orbital, an SP orbital is an orbital that has 50% S character and 50% P character. So this has much more S character than this compound. And recall that the more S character a bond or an orbital has, the more stabilizing or the more stable the electrons in that bond will be. And because this has much more S character than this, the electrons here are more stable. And therefore, this compound is more stable than this anion. And that means this reaction will be more likely to take place.