AFAIK, an affidavit is always required before an insurance company will collaterialize the policy.
If the man has complied with their policies, he should receive the benefit of the policy that they issued.
Granted the whole story sounds a bit fishy...like last month’s tuna out in the compost pile, but in the absence of proof to the contrary, the Insurer should pay up as per their policy.
They're out the same amount of money no matter who gets it. For them to file a lawsuit to avoid paying the husband is extra cost out of their pocket. They must be doing this on principle since it makes no business sense.