Good people can still be borderline retarded and a danger to themselves and those around him.
You will be kicking yourself for not acting immediately when they are destitute and begging YOU for help.
What would you (in her husbands shoes) want you (as yourself) to do? A marriage is built on mutual trust, love, and respect (afaik, I'm not married so what do I know). There is no trust to be had in that relationship. If the marriage is going to succeed AT ALL you need to show him they need to rebuilt because as far as he knows, he can and should trust her. If the marriage falls apart, it was going to anyways and they'd be a lot worse off financially.
Say these 2 things out loud to yourself:
"My bitch of an ex wife sent all our money to some fucker in Malaysia. I'm broke but now I still own half her debts."
and
"My bitch of an ex wife tried to send all our money to some fucker in Malaysia, but some nosy former coworker let me in on it. Cost me my marriage and $50k but at least I'm out."
Those are the 2 worst case scenarios. Pick one, because you hold the power here.