Improperly train the replacements, take the severance and then just not be available.
Better option would be for all the IT to get together and negotiate a much better severance package as a group.
Well, instruction manuals do get lost, and who could fault an ex-SunTrust employee for changing a few passwords, and then forgetting exactly what the new passwords are. After all, those ex-employees are under a lot of stress.
As for not being available, the contract mentions that the ex-employees must be "reasonably available". That is so vague as to be meaningless.
In other words, I agree with you.