An excellent question! The whole situation stinks, and therefore begs for investigation. If a definitive pattern emerges, hopefully, people go to jail for a loooong time.
That would be a Christmas present to the entire producing world, as it points out a fundamental problem in modern finance capitalism:
Hiring a "portfolio manager" is a right of free association. Once that entity gets so big that there are no alternatives to a retirement portfolio manager (they all seem to manage the same bundles these days) voting that stock then becomes opaque to the public; it alienates the public from the consequences of bad choices of management and allows collusive arrangements among corporate entities representing interests adverse to the suppliers of wealth. A good example would be gaming wars for fun and profit that puts the entire nation at risk and in debt. That's when the public's representatives then come back to the corporate finance to borrow money. There is no representation of voters at a bond auction. The principals inherent to economies of scale build an instability into that system wherein once an entity becomes so big that it is capable of manipulating the market. The efficiencies gained via competition are then lost, and aggregate wealth therefore declines. We saw this in the cases against ALCOA or AT&T. While the subsitution effect then dictates that consumers seek alternatives to suppliers of monopoly goods, when that good has no substitute, or is a fiancial stake so large that it absorbs those alternatives, the entire system then becomes subject to manipulation and therefore destroys aggregate weath.
Blackrock, Vanguard, Amazon, Google etc. are that big, and they all demand breaking up. Google should never have been allowed to acquire YouTube for example, nor Amazon into server farms. The system is begging for entities to be broken up. The gambit of sustaining a competitor to maintain the pretense of competition and also improve one's own competitive efficiency (Intel over AMD) does mitigate the game to a degree, but only out of fear of antitrust action by the DOJ.
This is not to even broach what needs to be addressed re the ability to wield financial power over representative government at those bond auctions. We really do need a good AG to lead us out of this mess.