Who was really responsible for the plauge of Europe

the French and there ships

Explanation:

they didn't keep there ships clean when they would trade to us and what happened was the rats decided to go in them because it wasn't clean, then the French would come over to us and give us many interesting stuff to sell but as they were doing this the rats had ran off the ships and boarded us then they started running around all over and because they were in the sewers they created a disease that they were spreading as well as them dying and it would be flees that had jumped on to the rats that then would jump on to us giving us this disease that had sadly killed around 250 million