What is the European gold fever?

/kloc-After the 5th century, due to the development of commodity economy and the germination of capitalist production relations in western European countries, European businessmen and feudal lords enthusiastically pursued money as a means of commodity exchange, eager to obtain precious metals for making money, thus setting off a crazy "gold rush" everywhere. Especially at the end of 13, after traveling in China, India and Southeast Asian countries, Venetian businessman Kyle Polo wrote a book "Travel Notes of Marco Polo", which was full of praise for the "golden land and wild spices" in the eastern world. This book was widely circulated in Europe at that time, which aroused Europeans' strong envy and yearning for the prosperous and powerful East.