Mythtery
Santa coming down the chimney is just a Muggle conspiracy to cover up that Santa is a wizard traveling by Floo Powder.
Evidence
This theory is born out of the correlation between Santa’s popular preferred means of travel – the chimney – and the operations of the Floo network as we know it. But as we go deeper down this rabbit hole, there’s some compelling evidence to back this theory.
Santa Claus is a mythical character originating in the Western Christian culture known to bring gifts on Christmas Eve in the form of toys and sweets for well-behaved children. He’s a jolly old man who wears a lot of red and fur and is a glutton for cookies and milk. Nothing too unusual.
But how does such a large man, with all his goodies in tow, manage to slide down something as narrow as a chimney? You guessed it – the Floo Network. What about the houses without the chimneys? Apparation, of course. As for his carriage, that’s easily explainable after we’ve seen not one or two but three locomotives (the Ford Anglia and Sirius’s motorbike) be charmed to fly, and one of them was even a carriage (the Beauxbatons carriage). Additionally, similar to Thestrals and hippogriffs, Santa’s reindeers could be another variety of magical aerial creatures native to the frigid North. A dash of Invisibility Charm to the mix, and we have the perfect conspicuous vehicle to fly around distributing gifts.
Then there is his sack of gifts. How does he carry all the presents for all the kids in that rather small bag? An Undetectable Extendable Charm perfectly fits into that explanation. And suppose someone were to accidentally walk in on him munching away at the delicious cookies laid out for him. In that case, he could simply use a memory modifying charm such as Obliviate to rectify it or use the Confundus Charm instead to make the parents believe that they had themselves bought the gifts.
Still, how does he manage to deliver these packages to millions of kids across the globe in one night? The delivery schedule is too tight to be feasible even after factoring in time zones and the convenience of Apparition. Unless you could simply stop time – or turn it back. Certainly, if a thirteen-year-old student can get her hands on a Time-Turner, it shouldn’t be a big deal for Father Christmas himself.
Santa doesn’t work on his own. In fact, he’s quite an entrepreneur. He has a whole workshop of toys set up at the North Pole, which he runs with the help of his trusty Christmas “elves.” This is perfectly in line with the wizarding tradition of employing house-elves as labor.
But why can’t we find Santa? Surely, a whole toy workshop should take up quite some space. But so does a castle, doesn’t it? It’s entirely possible that the Santa’s clever enough to make his premises unplottable and protected with many Muggle Repelling Charms. There’s also a theory that Santa’s blatant misuse of the time turner and memory modifying charms as well as his eagerness to interact with Muggles has been found in violation …….
Source: https://www.mugglenet.com/2021/12/mythtery-santa-is-a-wizard-travelling-by-floo-powder/