Why did Toyotomi Hideyoshi enforce isolationism and closed-door policy in Japan

To maintain supremacy and exert increased control over unified Japan

Explanation:

Toyotomi Hideyoshi rose to power and prominence uniting the whole of Japan promoted and enforced isolationism and closed door policy in Japan gain control over the country's foreign policy in order to maintain supremacy over other in-country powerful lords and guarantee social peace  to the people that have become used to war

The policy also helped increased the amount of taxes and levies collected by the Toyotomi treasury by Toyotomi Hideyoshi the then ruler of Nagasaki in 1587

In order to limit the challenges of religion to central authority banned missionaries from kyushu to gain supremacy over the Christian daimyos.

under god i have placed my chiest strentgh and the safe guard to my loyal subjects

these civilizations were located around fertile rivers, where they could produce an abundance of crops