Selfish plug here but this industry is our bread and butter (our company hosts the data rooms and powers the marketing for the vast majority of subprime auto backed securitizations in the US). Below is a link to issuance volume going back to 2008. You'll see that big banks are not the leading originators in this market and at peak (2016) we're talking $26bn in loans (versus hundreds of billions in subprime mortgages). Additionally, unlike mortgages on second and third homes, people are far less likely to default on a car rather than a home because in suburban America, you need your car to keep your job, regardless of where you live.
Finsight Subprime Auto issuance profile: https://finsight.com/sector/Auto/Subprime%20Loan