>The second one is only confusing because you're trying to find a cause and effect between 2 events that simply happened to happen at the same time

The author uses "because", which in context clearly indicates to me a cause and effect relationship.

Even overlooking that, "impecunious operation of the bank could cause the value of the mortgages to be impaired" is not addressed by your explanation. You explain how external factors could reduce the value of the mortgages.