What was the main reason Europeans were expelled from Japan ?

The spread of Christianity

Explanation:

Giving the freedom to let Europeans travel and stayed in Japan provided an opportunity for Christian missionaries to spread their religion in that country. By 1590s, these missionaries managed to convert more than 200,000 people into Christianity.

These Christian groups started to formed factions. These factions had the ambitions to put a Christian ruler/representation In Japan. The Emperor of Japan at that time felt that if He let the Christian influence grew, his position within the government would be threatened. This was the reason why he ordered Europeans to be expelled from Japan.

to contain the wave of communism

an economic reason that the south needed a reconstruction plan is that plantations, factories, and other businesses were destroyed during the war.