Giants like Apollo, Blackstone and KKR made their names in the business of private equity. But today, the thing that investors seem most excited about is growth in their private credit businesses.

Recent flows of money into what are now known as alternative-asset managers have often tilted toward alternative forms of lending and away from classic private-equity buyouts. Buyout fundraising has been slowed in part by the difficulty of exiting old deals. Real-estate funds have also been hit by worries about things like commercial property values.