The timeline suggests that after World War II, other nations felt the need to develop their own nuclear bombs. This is evidenced by the entries showing several countries (Russia, the United Kingdom, France, China, India, Pakistan, and North Korea) conducting their own atomic bomb tests following the initial development of nuclear weapons by the United States. The pattern illustrates a widespread proliferation of nuclear capabilities among various nations in the years that followed the war.
Therefore, the most accurate response is:
After World War II, other nations felt the need to develop their own nuclear bombs.