There has been good, recent, academic analysis of the success of Berkshire Hathway.
It appears that Buffett has discovered (or intuited) the 'low volatility anomaly'. Low volatility stocks outperform high volatility ones, in the long run (that corresponds to his dictum to buy good franchise businesses).
He also makes massive use of leverage-- as an AA rated insurer, he can in effect borrow from policyholders and capital markets at very low rates of interest-- low cost of funding means positive 'spread'.
For example electric utilities typically have an allowed rate of return of 8-9% on new investments. Buffett owns electric utilities, and is funding them from capital borrowed from the markets at 3%. A 6% spread-- that will grow your book value, even without further leverage. Something similar with railways (which are utility like but largely unregulated as to returns).
Similarly he lent money to the likes of Goldman Sachs and GE at 10% PLUS equity conversion rights, during 2008-09. He was a 'provider of liquidity'-- again investing in high quality business franchises when market sentiment was against them. Think the Washington Post Corporation ( I believe he is now over 10x book cost on that investment).
From the point of view of shareholders he does not charge the '2% and 20%' management fee + carried interest typical of Private Equity funds (which BH increasingly resembles). Studies show if he had charged hedge fund fees through his career, investors would have made something like 1/10th (from memory) of what they did make. Instead the management fees (central HQ costs) for BH are de minimis-- I believe head office has a stafff of something like 20? (might be 100-- most probably dealing with shareholder queries).
He has also minimized taxes for shareholders eg by avoiding dividends.
Now the thing about Buffett is he is unique. The autodidact of his era, a man who cared only for investing, his personal life has remained basically constant (same house, desk, old car, cherry Coke etc.) for his entire investing career. In some senses a high functioning autistic (now that we understand that autism is likely simply one end of a spectrum of human behaviour, rather than a pathology-- I recall working in an office where a woman, one of the most talented programmers, could only be communicated with through her teddy bear). Or as Benedict Cumberbatch (Sherlock Holmes in the brilliant recent TV series 'Sherlock') put it to a policewoman who called him 'a freak' : "high functioning autistic. Do your homework"
Human genius is like that. Every generation there is a confluence of conditions that throws up genius: Mozart, Beethoven, Monet, Handel, Leonardo etc. There has to be the right conditions (stock picking wouldn't have helped him survive WW1 on the Western Front) societally and historically. Had he been black,for example, or a woman, born when he was, it is unlikely he would have been given the chance to attend Columbia, study under Ben Graham, become a corporate leader, etc.
Those pre conditions having been set, then a sufficiently large society, whose conditions are met, will throw up a genius.
It's easy to see, going back to tribal groups on the plains of Africa, how such genius is beneficial to the group. The half ape that sees over the mountains and the empty Mediterreanean into Europe, and takes the tribe there, and those who remain die, when the climate dries up. Of course many such migrations will fail-- but one will succeed. One did
succeed, and Homo Sapiens began its long march out of its African birthplace to its domination of the world.
If we go back to the magnificent novel 'Watership Down'
by Richard Adams, then for every Fiver, who can see the terrible future, there is a Hazel, who can lead the rabbits out of danger to safety. Consider the duality between Buffett and Munger. Or Michael Eisner and (?) Frank Wills at Disney. Between Satoshi Honda and his sidekick, who used to tidy up after his messes.
The problem with Berkshire Hathaway is simply this: Buffett is not young. Neither is Munger. Time waits for no man.
He is the investing genius of his era. In fact, any era, for which we have enough hard data. But don't count on him being repeated.