Query about Question 13 from "(GRE Big Book) Test 1 Text Completion Problems (14)" [9704]

https://www.gregmat.com/quizzes/quiz/gre-big-book-test-1-text-completion-problems-14 (Question 13)


Can someone please explain the second blank?

From simple and uniform, it has changed into “not simple” and “not uniform”.

Differentiated basically conveys the idea that it changed into something that has many different parts that is something with great variety.