Private equity firms raise funds (usually have a 10yr investment horizon) and use these funds to serve as the equity tranche for a buyout that the remainder is financed with debt. Banks (or other investment firms sometimes nowadays) will provide financing for these buyouts and that financing is later refinanced with syndicated financing through loans or bonds.

There are a decent amount of banks that were in the middle of this process, covid hit, and they are now stuck with those loans on their books.