Why have so many of the new nations that emerged over the past half century struggled?

Many of the new nations that emerged over the past half century have struggled due to a combination of factors, including political instability, weak institutions, and economic challenges. The legacy of colonialism often left these nations with arbitrary borders and diverse ethnic groups, leading to internal conflict and governance issues. Additionally, reliance on a narrow range of exports and inadequate infrastructure has hindered sustainable development, making it difficult for these nations to achieve stability and growth.