misconception. There are many crappy ai imges of them falling through the cathedral floor. there are sources against that and also its very illogical. church ground is holy after all. the fall was most likely outside of a building, somewhat nearby the cathedral. also based on what we know it normally didnt smell. i mean imagin living somewhere and smelling poop every day. you will find a solution to block the smell rather quickly ^^
Naturally, because Henry VI went back in time and bought the architect an expensive dinner and suggest he place a trap door leading to the vast and disgusting sewers of Terserus right where the nobility of the Holy Roman Empire were standing!