Why did Greece retain its Christian faith under the Ottomans?

Answer 1

Most of Greece was under Ottoman rule from the fifteenth century until its Declaration of Independence in 1821.

Generally, the Greeks were not required to become Muslims, although many did so in order to avoid the onerous poll-tax imposed on non-Muslims. The "tribute of children" was a tax of children who were to be handed over, and raised as Muslims and enrolled in the Turkish army.

In the eyes of the Christians, those who converted were no longer deemed Greeks, but were considered to be Turks. Thus, 'Greek' meant Christian. By the 19th century, adherence to the Greek Orthodox faith became a mark of Greek nationality. So, after independence, those who had converted, voluntarily or otherwise, were not seen as Greeks.