The separation of church and state i.e secularism
If this is for edgenuity it is a) lack of organizational structure.
Did not like Western influence--traders brought Christianity and Western culture with them that the Chinese and Japanese did not like.
Western traders often came with goods and Christian missionaries. The influence of Christianity influence Asian cultures and was viewed as a negative to the culture of China and Japan. The isolation occurred as an attempt to remove Western influence from the countries.
