FYI: Ten years ago, Vanguard, American Funds, and Fidelity were the largest mutual fund companies, controlling 40% of the industry's assets. After those firms, there was a significant drop, with PIMCO placing fourth with 5% market share, most of which rested in a single fund ( PIMCO Total Return PTTRX).
The Big Three's ascendancy was logical. In aggregate, their funds had posted above-average performance, with below-average expense ratios (significantly below, in the case of Vanguard and American Funds). But, as the industry's disclaimer states, "past performance is no guarantee of future results." Perhaps investors had erred. Perhaps they owned funds that had once thrived, but no longer would.
Regards,
Ted
https://www.morningstar.com/articles/918990/the-biggest-mutual-fund-companies-have-indeed-been.html