Politics: Corruption within the government and spending money elsewhere is a big issue in some governments. The stability of a government has a huge impact on the countries ability to function. Also, the countries ability to invest in infrastructure and healthcare can be impacted by politics and how money is spent within a country.
History: colonialism has helped Europe develop, but slowed down the development of many other countries. On top of this, countries that began industrialisation have developed a lot more than countries that began it not so long ago.
Trade: The rich countries often exploit the poorer countries who can supply them with resources by paying the least possible they can for the product. However, since the poorer countries are desperate for trade links and money, they often have to accept being manipulated. Some countries have a 'debt trap' to the richer countries which slows development.
Aid: Aid can help some countries gain funding for projects such as putting money towards infrastructure or improving quality of life. However, too much reliance on aid can prevent trade links being formed.
Education: If the education is good in a country, the no. of people who can help in higher skilled jobs increases and development increases due to the skilled jobs e.g doctor, lawyer. Educated people then earn more money and pay more taxes, which can then be reinvested into the country.
Health: If the healthcare in a country is poor, then more people will get seriously ill and will be unable to do their jobs, limiting development. However, more money spent on healthcare means less money on development.