1) To celebrate Christmas.
2) To close the books of the current accounting year.
So santa bitcoiners ain't gonna save nobody's ass, and FYI, being a optimist doesn't make you Santa(bitcoiners)'s bitch, unless you're a hooker.
Nothing is actually certain yet, and like you said, many people always dump their stash on the market before the end of the year to celebrate Christmas, a lot can happen before then, so let's just assume Santa could come with the gifts before Christmas...
... Well, whichever way things turn out actually, who cares? The market has already been in a Christmas period for a while now with all the discounts he is giving to the smart ones to buy low, so it practically depends on each individual how they really want to be making the effort to stash up for the long run.
There is huge optimism in the air though for those who have always seen ember months as the month where things get to change hugely in the market with respect to increase in value of coins, but I guess this is something we will have to wait and see how things would turn out.
This optimism is the result of what crypto holders have observed in every year-end and nothing wrong on that. I mean when more people start believing something and start accumulating then market will not have any other option excepting reacting the way how most people do believe.