I think it may has to do :
1. Brk was approaching trillion dollar mktcap. Due to indexing, the bigger the mktcap, the more money for the index goes into the individual name with highest mktcap.
2. It’s almost certain Barron will have an article during the weekend talking about Buffett’s birthday and trillion dollar mktcap. People are front running the article.
3. A lot of call writing. Options are expiring this weekend. People need to buy new stocks or buy back calls to avoid their stocks being called away and pay capital gain tax.
4. investors are moving money out of the mega growth tech names into mega value names. Maybe there’s money flowing into financials (and that’s why Buffett is able to sell so many BAC), bringing BrK along, which is not really that liquid compared to other big names in XLf