The best order of events that explains the spread of Buddhism during Asoka’s reign is:
"Asoka took over Kalinga by force. Asoka rose to power through civil war. Asoka adopted Buddhism. Asoka became a just and compassionate ruler."
This sequence highlights the significant transformation in Asoka after witnessing the devastation of the Kalinga War, which ultimately led him to embrace Buddhism and promote its teachings of compassion and non-violence.