1. The next generation has been groomed by Buffet Himself, passing on as much knowledge as he can, but of course, this successor didn't create the fortune, doesn't appreciate it as much, and doesn't have as strong of judgement. However, he is surrounded by the old guard and wise mentors. But as those wither away, he is unable to determine who the worthy successors in his circle should be, slowly the inner circle begins to weaken too.

2. The next successor gets an even less effective set of principles from the first, only knowing off-hand how the money was made in the first place, they are a manager only. They also have no idea how the original people were selected or what makes a good inner circle. Soon it devolves into yes-men and people who seem superficially qualified to manage things.

3. The next successor has little no skills, other than showing up to meetings and going with what advisors say. Because the decision making of the original Buffet mentality has been so diluted, they only know superficial / surface understanding, akin to anyone who read the short books on the subject. They don't know how to do the deep diligence that made BH great. The inner circle is all sycophants, climbers, and clingers. Bad investments, debacles, and poor judgment create losses. Investors begin to panic sell, soon the BH stock crashes in value, losing 90% of the fortune.

And so on... Not hard to see how its like handing off a complex but successful open source project to your progeny instead of the most qualified developers. Pretty soon, its just an unmaintainable mess. They don't understand why things are the way they are, maybe they aren't as good a programmer as great grandpa. They definitely don't know how to hire and keep the best talent that originally built the thing. Pretty soon complexity budget and community good will are exhausted, people move to something newer and more dynamic.