Why had Japan cut off contact with Tang China at the end of the 9th century?

It is supposed that the missions ceased because conditions had become too unstable in Tang and because Japan no longer found it necessary to import aspects of Tang culture or conduct diplomacy with its neighbors. The emergence of an East Asian trade network may have played a part as well.

Explanation:

the revolution instituted a short-lived roman republic.

no one really purchased it themselves, it was all america, they had debates etc.