Obviously, I don't have access to the trial record, but that is highly unlikely. Motive is not an element of Art. 87. What the government is required to proof is that he missed it either through design or neglect - not why he was negligent or why he designed to miss it, just that he did.
However, the "why" is something that the prosecution can explore as an aggravating factor at sentencing. Are you sure that this isn't where this evidence was introduced?
Lakin could argue that the MJ was wrong when she allowed this testimony at sentencing. Of course, such an assertion wouldn't have any chance of prevailing on appeal because the government would be clearly within the boundaries established by MCM to raise such motivation at sentencing.
But, the "why" he did it with respect to the finding of guilty, is wholly irrelevant to the appellate court.
Motive is not an element of Art. 87. that the government is required to prove. All that is required of the government is that he missed...
It was introduced today according Mr Leftest blogger Sullivan. It certainly wasn't used yesterday by the prosecution when Lakin pleaded guilty to the other charges.