You’re going to get a LOT of reductive and low effort answers from Lemmy radicals. But this is a super complex question, and there’s not a 5-second ELI5 answer if you really want to understand.

Also, when the radicals scream at you, there’s going to be a core of truth. They’re going to yell about colonization and empires. That’s a major factor, but not an exclusive one. However, for getting radical and rabidly furious its all they’ll bother posting to you.

Things to investigate, because answering this for yourself in a meaningful way is going to take a while and require study. Here are some topics but NOT an exhaustive list:

1. Colonization

2. Resources (natural and otherwise)

3. Schooling, education, etc.

4. Stability, politically and otherwise (note this will have overlap with colonial and non-colonial powers destabilizing things intentionally for geopolitical gain)

5. Infrastructure (transportation, economic, water, medical, etc.)

6. Medicine as regionally practiced, traditional vs based on the the scientific method.

7. Geopolitics (isolationism, etc)

8. Geography (i.e. the US’s greatest asset is its location, it neighbors no enemies and its main enemies are separated by an ocean. One of the key reasons the US focuses on the ability to project force)

9. Religion

10. Corruption (politically and non politically)

11. Crime and non-military/nation based violence (also could get grouped under personal safety and security)

And again, honestly, a lot of these topics will overlap, but that’s what I mean by there isn’t a quick, easy answer.

And the reductive stupid answer is just yelling colonialism.

There’s a reason people get PhDs in this subject. It’s not a quick, easy question.

In this topic: people who underestimate the importance of infrastructure and low crime and low corruption.

1st answer: developing countries don’t have enough infrastructure to benefit from wealth. Not enough trains to move raw goods around, not enough roads or not enough electricity to do anything even if those good arrived.

2nd level: when governments get the money for such projects, they steal it from the people through corruption. See Turkey and all the invested dollars on earthquake-proofing buildings, it was all stolen in ways people didn’t understand or realize until the earthquake happened.

3rd level: even if the government didn’t steal the money, criminals can. Even in the USA we deal with transformer thieves (transformers are bundles of copper that convert long distance high voltage power into short distance power for houses). These copper bundles can sell for $$$$ in the black market.

So even if #1 and #2 miraculously happen, a criminal will steal the infrastructure and they gotta start all over again.

Everyone knows how to make cities more advanced and better. Build highways, trains, mass transit. Invest into freight (trains or boats). Invest into education so that people can run these machines.

And many 3rd world countries advance forward. But it’s harder to do than it looks.