What caused Greek to lose their freedom?

Greece lost its freedom primarily due to the Ottoman Empire's expansion during the 15th century, which culminated in the fall of Constantinople in 1453. The Ottomans established control over Greek territories, enforcing their authority and imposing heavy taxation. This domination lasted for nearly four centuries, during which the Greek population experienced significant cultural and economic repression. The struggle for independence eventually led to the Greek War of Independence in the 1820s, which resulted in the establishment of a modern Greek state.