David Kane is the CEO of Kane Capital Management, a far cry from a serious university researcher. This is hardly the kind of person who does serious scientific research that get published in the Lancet. On ther other hand, a CEO is precisely the kind of person to have vested interests in the Iraq war.
Further, what Kane has submitted is not even a "study". It is merely a comment, i.e. a minor issue. Also, "submitted" does not necessarily mean "accepted". Given Lancet's high standards, only a small fraction of submissions get accepted for publication.
Even if this minor comment were to get published, the original authors of the Lancet casualty study can always clarify the soundness of their methodology.