Hitler had a problem with religion. Judaism, of course, but also Christianity, because their Messiah was a Jew. And although he never aspired to replace religion with Nazism, he had a problem with Christmas. You can't ask the German people to not celebrate Christmas, but the Nazi party had their own ideas about turning it into something that would further their own agenda.
Christmas, one of the most important dates on the calendar for German Christians, offered the perfect target for this sort of co-opting. And so, no matter what any one Party member thought of Christmas or Christianity, the holiday was recast in the Nazis’ own image shortly after their rise to power: A holiday of blonde-haired, blue-eyed Aryans celebrating ‘Nordic’ traditions that pre-dated Christianity and were anchored in their native land. (The Nordic race was a racial subcategory created by anthropologists in the early 20th century. It was a branch of the Aryan race, which belonged, in turn, to the larger Caucasian race. Nordic Germanic peoples were, in the eyes of the Nazis, the master race.)
The Nazi version of Christmas meant new words, new symbols, and new customs. Read the specifics on the holiday Germans under Nazi rule celebrated, which is very different from our idea of Christmas, at mental_floss.