It is a systemic risk because its size and credit risk is opaque, like mortgage-backed securities were in 2008.

Banks needs to disclose the % of non-performing home, auto, business loans to rating agencies and regulatory bodies so their credit risk is known, and so regulators they can set rules on how loose or tight lending criteria should be in the industry. With 'financial innovation' like tranched mortgage bonds rolling up thousands of mortgages at various levels of credit risk into one, they can be traded without anyone actually knowing what the default risk is.

With private credit, there is no disclosure requirement because the lenders are not banks. PC is financing the entire AI datacenter boom, without which GDP growth in the US is effectively zero. If PC defaults rise, the bottom could rapidly fall out of the S&P 500, which is already being hit by the oil price crisis, and affect people's 401Ks and retirement savings.