As the famous theory of Diamond and Dybvig explained, institutions that have long-maturity assets with uncertain returns and short-maturity liabilities that are intended to be risk-free are innately subject to devastating runs.
After combing through MBIA's books, Warburg Pincus' partners concluded that marking to market the mortgage bonds it insures produces some scary numbers but doesn't threaten a firm that plans to hold the liabilities to maturity.
Sergio Trigo Paz was having conversations with multiple investors that planned to hold debt to maturity, and were matching the income flow from the emerging market bonds that they were buying to specific liabilities.