Answer:
- Stronger European nations
- Vikings considered raids to be not as profitable anymore.
Step-by-step explanation:
- Stronger European nations.
Viking raids started from around 790s to the late 11th century. At the beginning, European consisted of smaller kingdoms that had no affiliation toward one another. This made it easier for the Vikings to attack and conquered their territories.
As the conquest goes on, European nations realized that they need to joined forces and centralized their military's in order to fight off the Vikings. As a result, it gradually became harder for the Vikings to raid other European territories.
- Vikings considered raids to be not as profitable anymore.
As other European nations grew stronger, The Vikings realized that the amount of death/casualties that they face from each raids surpassed the economic worth of goods that they're able to steal. So they eventually decided to focus on trading rather than raids.