Remember, the bull market has just begun,

The analysis is quite good and worth a look:

The understanding of the Christmas market mainly comes from the perspective of taxes, looking at the behavioral psychology of most retail investors. Since the U.S. tax reporting is due on December 31, any trades settled before that date will affect the capital gains of that fiscal year. If you sell stocks with significant profits, you will face additional capital gains tax (especially short-term capital gains tax within a year, which can be quite painful). Conversely, if your stock account ends up with losses this year, part of those losses can offset your taxable income. This is why wealthy individuals choose to borrow against their stocks instead of selling them when they need cash; they want to minimize taxes. The interest rates on loans are much lower than capital gains tax, allowing them to continuously roll over debt, effectively deferring capital gains taxes indefinitely. They always have money to spend without paying taxes.
Sorry for digressing 😂
Most retail investors actually share a similar mentality. They tend to sell their highly profitable stocks in December and then have to quickly pay taxes in January. Typically, you wouldn't do this unless you urgently need cash; it's better to close out losing positions to offset taxable income. Therefore, stocks in the market can suffer from extreme conditions—those that are doing well continue to thrive, while those that are underperforming struggle. If a stock performs very strongly throughout the year, it generally continues to rise in December due to fewer sellers. However, if a stock has not performed well this year, it may continue to weaken in December as sell-offs occur to lock in losses.
Similarly, looking at BTC, it is undoubtedly one of the strongest assets this year. Therefore, the likelihood of selling BTC stocks, ETFs, and Coinbase/Robinhood holders in December is low; it may even continue to show strength, which is reasonable. However, one must be particularly cautious in January. So if you're planning to short before then, it's best to focus on day trading and take profits quickly, as the declines may not be smooth and could be limited.