Well the Banks hire their appraisers, so they are still responsible for the appraisal and also the ones responsible for securing, guaranteeing and issuing the Mortgage Loans

But also greedy banks were selling too many loans such as Interest Only or Adjustable Loans to people who couldn't afford Conventional on over inflated home prices. Then the Fed raised fed funds rate six times reaching 2.25 percent by December 2004. It raised it eight times in 2005 rising two full points to 4.25 percent by December 2005. In 2006 the new Fed Chair Ben Bernanke raised the rate four times hitting 5.25 percent by June 2006 then when the prices fell in 2006, people with Adjustable or Interest only loans couldn't afford their payments any longer or sell their property for profit because it wasn't worth what they paid for it, which then triggered a ton of Loan Defaults causing the 2008 Housing Crisis and one of the worst recessions since the Great Depression.
2020 Banks were doing it again