Is this small passage correctly structured and worded?

Is this small passage correctly structured and worded, particularly the "not because...unsuccessful" part? FYI- Menzoberranzan is the drow city. As Drizzt neared the end of his training with Zaknafein, one of the lesser Houses of Menzoberranzan unsuccessfully attacked another. Drizzt and the other drow nobles gathered together to witness the city’s Ruling Council command the instructors and students of the Academy to immediately destroy the House that had launched the failed assault, not because they had assailed another House, but because they had been unsuccessful. Drizzt was horrified by the brutality of the Ruling Council’s so-called justice and the lesser House’s annihilation, and he would forever hold this against drow society