I've expressed before that Berkshire is not the animal it once was, primarily not because of its size but because Buffett is no longer the contrarian he once was.
He has amassed a huge stake in the world's most popular stock, Amazon in recent times. ...
I think there's more correlation between those than you expect. Look at some numbers...
According to Vanguard, the U.S. stock market grew about +9% per year for the last 3 or 5 years.
Berkshire Hathaway has a market cap of 450 billion. Doesn't that mean Berkshire needs to make $40 billion in profits per year, just to keep up?
Take the 400th biggest public company, Godaddy Inc. It's about $55/share with an average trading volume of 1.5 million shares/day. So Berkshire can't buy $80M a day of this company - that would double the trading volume by itself, and send the stock spiking upwards. So maybe... $10M a day?
Godaddy has an $8B market cap, so anyone owning over $400M has new filing requirements. So maybe Berkshire can buy shares for a month, have $300M ownership, and stay under the 5% level. Even if that stock doubles, that's a $300M profit for Berkshire, while needs a $40,000M profit to keep up with the market. It's not even 1%, after it doubles, and it takes a month to invest in it (to avoid sending the stock price spiking upwards).
That's the situation if he buys the 400th largest company, even if he knows they will double in value. Anything smaller or with less upside is even harder to consider. Berkshire has to limit which companies they buy, in order to make a difference to their profits. So I think becoming less contrarian is a natural by-product of their $450 billion market cap.