For the same reason Dorothy Loudon won for leading in Annie, Daisy Eagan won for featured in The Secret Garden, and Christine Ebersole won for leading in 42nd Street.
Because.
"What can you expect from a bunch of seitan worshippers?" - Reginald Tresilian
That show had lots of potential nominees and the producers wanted to spread them out in the categories to allow for more of them to be nominated. Also, several of the roles are on the cusp and could be considered either lead or featured. So the Administration Committee went along with the placements that the producers determined.