Complex sentence: Because of the established situation, divine culture, they all did not believe the new philosophy, Paramatma (Tripurasura) called his devatas and they started launching different weapons on the newborn baby.
Split into simpler sentences: Because of the established situation, divine culture, they all did not believe the new philosophy. In order to prove to the people this philosophy is true Suddhodana baby's Paramatma (Tripurasura) challenged his devatas and they started launching different weapons on the newborn baby.