When the housing crisis sent the American economy to the brink of disaster in 2008, millions of people lost their homes. The banking system had failed homeowners and their families.

New investors soon swept in — mainly private equity firms — promising to do better.

But some of these new investors are repeating the mistakes that banks committed throughout the housing crisis, an investigation by The New York Times has found. They are quickly foreclosing on homeowners. They are losing families’ mortgage paperwork, much as the banks did. And many of these practices were enabled by the federal government, which sold tens of thousands of discounted mortgages to private equity investors, while making few demands on how they treated struggling homeowners.

The rising importance of private equity in the housing market is one of the most consequential transformations of the post-crisis American financial landscape. A home, after all, is the single largest investment most families will ever make.

Private equity firms, and the mortgage companies they own, face less oversight than the banks. And yet they are the cleanup crew for the worst housing crisis since the Great Depression.