Kerry Killinger, Washington Mutual’s CEO since 1990, was fired by the board of directors Sunday. The mortgage crisis, surprise surprise, was the culprit:

Critics charged WaMu put itself in an especially difficult position by its acquisition of a mortgage company that specializes in loans to people with poor credit histories. That segment, known as the subprime market, was the first in which problems appeared. WaMu also loaded up on other risky types of lending, such as option ARMs (adjustable rate mortgages), which allow borrowers to set their own payment, even if the result was that the principal actually grew from month to month. In addition, WaMu’s mortgage business is concentrated in hard-hit states such as California and Florida.

Weakness also is starting to show up in WaMu’s portfolio of more conventional home loans, as well as in home equity lines of credit and credit cards.