Why did Bai Juyi's poems have a great influence on society in ancient times?

Bai Juyi is a poet with great influence. His poems were widely circulated at that time, and his simple and straightforward poetic style was affirmed and imitated by many literati, which had a great influence on society. His poems have also spread to frontier minority areas, even as far away as Korea, Japan and other countries, which have had an important impact on his literary development.