One lesson to learn from this case is that when planning your estate, you can often decide whose inheritance portion should pay the estate taxes. However, when blended families are involved, that type of decision is likely to lead to acrimony. It should, nevertheless, always be clear to your heirs what your intentions are and why. At a minimum, it needs to be clear to the executor and to the person who drafts your estate plan.
In this case, it is possible Clancy told his wife that his intentions were to do one thing, but that one thing was not communicated to his lawyer.