I dunno, it makes sense to me? A savant is someone considered to be highly skilled, which generally comes with the assumption that they're quite smart overall. Idiot savant (as separate from the "savant syndrome" definition) implies a savant who lacks that general level of intelligence, because they have focused so much on one subject area that they've sacrificed all understanding of any other subject area (most genuinely smart people have at least a baseline understanding of areas of study outside of their own). It may not be the most elegant way of describing such a person, but for an article headline, it's short and to the point, conveying the right meaning in the fewest words possible.