Complex sentence: Her concert series, "Butterfly Kiss", was deemed by the media as a success, being a "milestone for all female idol singers" where the Korean market stigma mostly viewed that female artists would not be as commercially successful as the male counterparts.
Split into simpler sentences: Her concert series, "Butterfly Kiss", was deemed by the media as a success, being a "milestone for all female idol singers". It helped defying the deeply-held Korean market stigma that female artists would not be as commercially successful as the male counterparts.