Santa is a stand-in for Jesus... for children. They're both magical beings that can perform miracles and have similar methods: Both Santa and Jesus have naughty lists and forms of punishment that come later; much later (both are equivalent lengths of time to a child though 🤣). Both bring "gifts". Both have traditional appearances. Both have followers that wear silly hats and strange clothes. But most importantly...
Both are imaginary.
If you believe in Santa as an adult you're ridiculed. If you believe in Jesus as an adult you're just labeled, "Christian". Yet the fact that nearly every child eventually finds out Santa isn't real is quite disturbing to a lot of Christians. After all, if they could stop believing in Santa--who is so similar to Jesus in every way--then they could stop believing in Jesus.
There's a lot but here's a reasonable one:
https://www.yahoo.com/news/trump-threatens-defund-schools-teach-155006275.html