My general understanding of this is that ‘Xmas’ is what people write when they don’t believe in God or Jesus, or follow Christianity but they still celebrate Christmas.
So they shortened it to Xmas which removes the religious part of the title.
Obviously nowadays I think people just use it because it’s easier and they don’t put much thought into it.
I could be wrong though, it could just be entirely a business thing
What do you guys think?