As I mentioned, AIG had about $ billion in commercial paper outstanding, so its failure would have exacerbated the problems of the money market mutual funds. Another worrisome possibility was that uncertainties about the safety of insurance products could have led to a run on the broader insurance industry by policyholders and creditors.
Moreover, it was well known in the market that many major financial institutions had large exposures to AIG. Its failure would likely have led financial market participants to pull back even more from commercial and investment banks, and those institutions perceived as weaker would have faced escalating pressure.