Tax proposal - The big money for PE players come primarily from "carried interest" which is 20% of gains they generate from buying companies and reselling them
through IPOs or sales to corporates or other private equity firms. The firm pays capital gains rate of just 15% on them, as compared to 35-45% tax levied on corporate earnings. There is a proposal in US congress which would tax carried interest at regular income tax rate of 35% instead of present 15%. And this proposal, if implemented, would take a major part of their earnings.

End of Cheap Money with rising interest rates - Instead of using their own money, PE firms raise money from other sources and invest them. However, with interest rate marching upwards, it will be harder for PE firms to raise money for further investment and that signals that the private equity boom may have peaked.