The main reason why some Southwest Asian countries have become wealthy in the last 100 years, while their neighboring countries have not is because of two very important resources: oil and water.
Oil and natural gas has made several countries in the Middle East very rich. Although it may be confusing, the Middle East is also considered to be part of Southwest Asia. Since so many countries have a demand for these resources, countries like Saudi Arabia, Iraq, Kuwait, and Iran have made a lot of money from selling these resources to other countries around the world.
Countries that do not sell a lot of oil are also poor because of the lack of water in their countries, as well. Irrigation is necessary for crops and livestock. The lack of water in the area makes it hard for farmers to produce enough crops to make an adequate living or feed their population. Farmers also have used chemicals and fertilizers that contaminate the little water they have. Access to water has caused a lot of fighting in this area, as well.
Qin Shi Huangdhi was the king of the state of Qin, hence the title of Qin in front of his name. A big thing that he did was unify China in 221 BC after he conquered all of the other warring states in the China region. He brought peace and prosperity to China after that. Hope this helps.