The book, which is the source of this passage, was written in 2014. Why did the author use enters in the sentence?
By the beginning of the 20th century psychology as science had barricaded itself against any liaison with culture. The focus on experimental psychology of lower psychological functions was expected to make psychology a real science. Linkages with history in general and cultural history in particular would have been obstacles on the royal road to scientific purity. The result was another century of no serious work on complex cultural phenomena by psychologists. Music — a favourite topic for early psychologists in the 19th and early 20th century — has not been a prominent research field as the discipline enters the 21st century. The story is similar in the case of religion, which in its various forms frames social and personal lives all over the world. It had mostly been abandoned by psychologists as a research field by the 1920s. Nearly a hundred years later, our lives are filled with ever re-emerging spiritual sentiments that are easily captured by new religious organizations.