Some scholars -- including Ubayy ibn Ka'b, one of the Prophet's most distinguished companions and reciters -- reportedly treated Sura Al-Fil and Sura Al-Quraysh as a single unit. They are not a single sura in the standard Uthmanic text, but the theological case for reading them together is overwhelming. Al-Fil provides the premise. Al-Quraysh draws the conclusion. Together, they form the Quran's most concise and complete transactional argument: God did this for you, therefore you owe Him this.
The connective particle that opens Al-Quraysh -- the Arabic li-ilafi -- is grammatically linked to what came before. "For the security of Quraish" 106:1. For their security. The word li indicates purpose or cause. But the purpose or cause of what? The most natural reading, endorsed by Ibn Kathir and many classical commentators, is that it refers back to the destruction of the elephant army. God destroyed Abraha's forces for the purpose of securing the Quraysh. The miracle of the birds was not an abstract demonstration of divine power. It had a specific, practical beneficiary: this tribe, these people, this economy.
"Their security during winter and summer journeys" 106:2. The Arabic rihlat al-shita' wa al-sayf refers to the two great annual trade caravans that formed the economic backbone of Meccan society. In winter, the caravans travelled south to Yemen, where they traded with the markets connected to the Indian Ocean and East Africa. In summer, they travelled north to Syria, accessing the Mediterranean trade networks and the commerce of the Byzantine Empire. These two routes -- south in winter for warmth, north in summer to avoid the desert heat -- made the Quraysh the commercial middlemen of the ancient world.
But these trade routes were not secured by Qurayshi military power. The Quraysh were not a great military tribe. They had no standing army, no fortified borders, no system of garrisons along the caravan routes. What they had was the Kaaba -- and the sacred status it conferred. Because the Quraysh were the custodians of the House that all Arabian tribes revered, their caravans were granted safe passage through territories that would otherwise have been hostile. Raiding was the economic norm of pre-Islamic Arabia. Every tribe raided every other tribe's caravans. Except the Quraysh. Their caravans were sacrosanct, because attacking the custodians of the Kaaba was an offence against the sacred order that even lawless tribes respected.
God is making a precise economic argument. Your wealth comes from trade. Your trade depends on safe passage. Your safe passage depends on the sacred status of the Kaaba. And the Kaaba's sacred status was confirmed -- spectacularly, publicly, undeniably -- when I destroyed the army that came to demolish it. Your entire economy is a chain, and every link in that chain leads back to Me. "Let them worship the Lord of this House" 106:3. Not the house. The Lord of the House. The distinction matters. The Quraysh worshipped the House itself -- or rather, the idols they had placed inside it. God is redirecting their attention from the structure to its Owner.