Why were the years of the crusades so violent?

Because they were primarily started to secure control of holy sites considered sacred by both groups.

Explanation:

The Roman Catholic Church wanted to take back the holy land from Islamic rule during medieval times. To do this they perfomed many "crusades" resulting in estimated millions of death.

that is because lower interest rates allowed people to work harder to make money. it multiplied like that and now the uno(not the game) is very strong.

i like trains

it affected it because the kingdoms (with trade) slowly got richer and richer.