The Mishnah (Pesachim 116a), when recording the Mah Nishtanah, phrases the question as:
מה נשתנה הלילה הזה מכל הלילות?
The most literal translation I can muster from this is:
What is different this night from all nights?
- The Mishnah clearly doesn't mean "What is different on this night from all other nights?" as the questioner proceeds to elaborate the differences: we only eat Matzah, we only eat Marror, etc. Perforce, the Mishnah must mean "What is it that causes this night to be different from all other nights?" So why doesn't the Mishnah just say that - למה נשתנה הלילה הזה, "Why is this night different from all nights?"
- The wording of the end of the question is similarly awkward, contrasting this night to "all nights." Clearly it means all other nights, so why doesn't it just say that: משאר הלילות? (This question would similarly apply to the later stitches, where we say שבכל הלילות, "for on all nights," instead of שבשאר הלילות, "for on all other nights.")