Santa Claus, or more properly Saint Nicolas of Myra is one of many early church saints whose legend is better known than any historical facts. As many other saints revered in the Catholic Church, he was moved around in the calendar during the reformation instigated by Martin Luther. The reformers ditched the saints' days and he therefore started to appear on Christmas or New Year instead of December 6. As an early church saint, his devotional day is also strongly rooted in the Orthodox churches of Eastern Europe.
When Emperor Otto I went looking for a wife for his son, he wanted it to be a political statement. As the first Emperor from German stock, he was looking for acknowledgement by the other half of the Roman Empire. A princess of the house of Byzantium it had to be and nothing less. Once that goal was achieved, the newcomers went out of their way to show how much they appreciated the gesture.