How did trade with the venetians contribute to the fall of the byzantine empire?

They all have helped

Explanation:

It’s stated

Explanation:

Initially located at the coastline Northeast of what is today  Italy, these group of people had been part of the Roman Empire since about 49 BC.  They vulnerable to attacks from the Franks and the Huns and ended fleeing to the islands, away from the lagoon area thus building the first structures of what is today known as Venice. They remained as Romans nevertheless; they were ended up governed by Emperor Justinian of the Byzantine Empire who used to be part of the Eastern part of the Roman Empire until the fall of Rome at about the 5th century.

The Venetians grew as important traders and had an import port, which traded extensively with the east thus making Venice important for the Crusaders who were increasing their invasion activities eastwards.  

This this importance eventually led to a political treaty signed between Venice and Byzantine Empire in 1082. Consequently, Venice gained a stronger economic and political presence within the Byzantine Empire.

When the Normans attacked the Byzantine Empire at Constantinople, their capital (present day Istanbul), they needed the help of the Venice´s fleet of ships to defend  their city.  

The Venetian citizens were well rewarded with annual financial grants, grand titles and an important commercial clause, which granted them, the Venetians, a trade status in Byzantine in 1171, however this close relationship grew soar after the accusation of treason by Byzantine Emperor who had the Venetian citizens imprisoned as punishment and revenge. Though the then Doge of Venice tried, several peace agreements the angered Venetians demanded war and so Venice with the help the Crusaders in 1204 had Constantinople invaded and looted.