There are many reasons throughout history as to why a city was named the capital of an area or country. They may have been the most populous or the best location. Nevertheless, some of the capital cities have remained for many years whereas others have been moved for different reasons. Sometimes, these forward capitals, which are the cities that have been moved, was due to having too many people making the city overcrowded and increasing its crime rate.
For example, Brazil moved its capital from Rio de Janeiro to Brasilia. Rio de Janeiro is located on the coast. Since the coast is a popular place to reside anyway, making this the capital make it much more crowded. So, Brazil moved the location away from the coast and more inland.
A forward capital is a symbolically relocated capital city usually because of either economic or strategic reasons. A forward capital is sometimes used to integrate outlying parts of a country into the state. An example would be Islamabad.