The Fedora Faction might argue that believing in Santa, Rudolph etc. is not any more irrational than believing in God and Jesus *). Only the latter is socially accepted, that former not -- but autistic people often don't get what's socially accepted or not, so Santa it is.
I did believe in Santa until an above-average age, that is, into my early teens. I imagined him in a kinda science-fiction-y way, as a quantum mechanical phenomenon. Of course, later I became sceptical; but I once met a girl who told me she believed in fairies and elementary spirits until she was 19. She came from an anthroposophist family - in this culture belief in magical beings is widely accepted.