How did the Turks come to topple the Byzantine empire?

The Turks toppled the Byzantine Empire when they defeated Byzantine forces in Constantinople in 1453. The Ottoman Empire forces or the Ottomans were led by Sultan Mehmed II. The defeat of the Byzantines in Constantinople followed a 7 week siege of the city and led to a massive blow to Christendom because the Ottomans continued to advance into Europe in establishing their massive empire.