Is Vajrayana the fastest and only way to enlightenment? Bön & Shaivism

Why is Tibetan Buddhism the fastest way to enlightenment? What is the difference of Kashmir Shaivism and Nyingma School? Why is Tibetan Buddhism faster and the only way? Tibetan Buddhism developed from traditional Bön and Together with Kashmir Shaivism, and traditional Buddhism was imposed to the Bön tradition. Why was Buddhism better than Bön Religion? Why did Buddhism adopted the lucid dreaming of Bön Religion if it was better? Am I missing something?