My focus will be on Kukai and Esoteric Buddhism and why it gained more traction in comparison to the other sects.
Kukai (774-835) was a Japanese monk born into an aristocratic family was trained in the Confucian Classics. He became disillusioned with confucianism and ended up leaving with a monk and began schooling in China and learned from various teachers. He later went back to Japan founded the esoteric school of Buddhism in Japan. Shingon remains one of the largest schools of Buddhism in Japan. The teachings in esoteric practices involving meditation, visualization, chanting and ritual. In Esoteric Buddhism, the practices engage body, chants and the mind to help the student experience Buddha-nature eventually experiencing the enlightened being through the