Surah Quraysh follows straight on from Surah Al-Fil, the story of the elephant army that came to destroy the Kaaba — and was stopped by little birds carrying stones.
The two surahs fit together like two halves of one sentence. Al-Fil says: Allah protected the Kaaba. Quraysh says: and that is why you are safe, and why your caravans travel in peace.
So Allah is saying: you have already seen what I did for you. Now worship Me alone!