Poor countries and mismanagement

Why are poor countries poor? Is it because of corruption or mismanagement or trauma from colonial occupation or whatever conspiracy theory you can throw it. The people and governments in the poor countries blame the west since it is much easier to direct criticism to them then to themselves. I have studied poor countries (on the internet and being physical in countries) and I believe that despite blaming more of the poverty on the corruption, it is really the mismanagement of resources that is mainly the root cause of their poverty. Poor countries are rarely short of natural wealth and the means to get it since their population is hard working. It is just that these resources (human and natural) are so mismanaged that they end up leaving the country in more mess than it started with. The people who manage these countries don’t want to manage their resources in an efficient way since if things start to move smoothly then what is the purpose of them being there in the first place. I am not saying that people are not corrupt but with the amount of wealth the poor countries have, even with corruption, if only the mismanagement of the economy can be controlled and sincere and honest people are installed who can effectively manage the economic and human resources of the country, then there will be less blame to go the colonial powers (it will still be there out of habit) and effort will be put to taking care of their country