Why did Western Europe slip into the dark ages?

One of the predominant reasons for collapsing the civilization in Western Europe and slipping the whole part in the dark ages is the Fall of the Roman Empire.

The Central government was vanished from the fall of Rome rules disappeared. Moreover, the countries went into intense chaos who were under Roman control.

The laws were vanished soon after the Roman empire's disappearance, due to which people started living a life by their own rules. The weaker section of the society was working for them, whereas the robust section took control of the resources.

Illiteracy developed in western Europe as most of the resources went to soldiers and farmers, which made it very hard to fund education.

According to some people's theory, it is said that the church's approach towards learning was the significant reason for the collapse of civilization. It is believed that one of the primary reasons for the fall of the Roman empire was the abuse of Christianity. (See Why is Christianity popular in Europe?)

Feudalism was a system that emerged with the fall of the Roman empire. As per this system, the stronger section of the society takes over a piece of land and provides labor and protection to the weaker section of the society, in exchange.

As education was not a priority, due to which some people cited the invasion from Barbarian tribes. It is still believed that one of the major causes of the Dark Ages was those invasions.

Tribes became the enemy of each other and started fighting to survive amid the fall of the Roman Empire. The reason to compete with one another was, the Roman army was there to protect those tribes earlier, but now as the empire collapsed, those tribes felt unsafe and became aggressive.

The Plague arrived in Europe that deteriorated the civilization enormously.

With the Fall of the Roman Empire, the network of trade set up by them was also collapsed. This made the situation worse. (See Video Summary: 1943 Axis losing in Europe)

By misusing their power, the robust section and the rich people of the society changed the community structure by implying the power of the sword. The made the whole order disrupted in western Europe.