As the main battlefield after World War II, why did Europe become a net migration area?

First of all, Europeans who fled during the war have already returned home. Secondly, European powers such as Britain and France have many colonies overseas. After World War II, because of its weak strength, it was either actively decolonized or forced to retreat. At this time, their nationals in the colonies also returned to China in large numbers, and some leaders of the colonies also entered Europe.

Then, although Europe suffered great trauma in the war, its position as one of the most developed regions in the world remained unchanged, especially its advanced science and technology, a large number of high-quality labor and talents, and the assistance of the Marshall Plan of the United States. The European economy recovered rapidly and the world economic powers still gathered in Europe. Then a large number of people from newly independent countries, especially African countries, immigrated to Europe in large numbers. You know, Europe is stable at this time, but many places in Africa and Asia are at war.