Why did the Black Death spread so far and kill so many people?

Europe between 1347 and 1400. It was a disease spread through contact with animals zoonosis, basically through fleas and other rat parasites at that time, rats often coexisted with humans, thus allowing the disease to spread so quickly.

Explanation:

it was on the rise and doing very well and would continue to do well until the great depression from 1929-1939