It's not that Turkey celebrates festivals of one religion only. It is a multicultural country and its relationship with Santa Claus will explain why this country is also famous among the Christians of the world.
The 6th of December sees the St. Nicholas festival in Demre. Improbable as it may seem, it is the same saint who is reincarnated in the mystical figure of Santa Claus and brings Christmas presents to children all over the world. Not too much is known about the original Nicholas, other than that he was a bishop who, in the 4th century, lived in Myra, which today is Turkey. He died on December 6 in that town and his remains are buried in the Martyr Church. On the other hand, maybe not, because legend has it that in the 11th century, pirates from Bari, Italy vandalized the church and stole his bones. Nevertheless, relics or not, December 6 is the occasion for a cheerful festival to commemorate the saint. His connection to today's Santa Claus as the harbinger of gifts is, again, a matter of legend.
The famous story goes that the Bishop Nicholas heard of a poor man who had three daughters he was unable to marry off, because he couldn't afford their dowries. Since he couldn't continue to feed them either, he decided to sell them off to a brothel to earn their keep as prostitutes. Nicholas heard about their plight and secretly threw three purses full of gold through the poor man's window to save the girls from disgrace and a terrible fate. Of course, he was discovered as the benefactor, as otherwise, there wouldn't be a festival.
These unusual holidays and festivals of Turkey have, today, become an integral part of their culture and society.