Play around with this:http://https://www.opportunityatlas.org/
What you are describing are exceptional people from abroad. If you ran the numbers, you'd find that an infinitesimally (<-had to look that spelling up) percentage of the population of any of those countries actually does what you are describing. That's not unlike moving from poor to not poor/middle class/rich in the US. Possible, yes. Probable, no. It takes an exceptional person who is also presented with the exact right circumstances. Here is a real life example. I have a friend from Cameroon Africa who is finishing his masters degree and planning to go back to Cameroon to help others. Years ago, he got "lucky" and won a lottery in Cameroon. That got him a one way plane ticket to New York. He bounced from NY to AL to TX sleeping on couches of people that had some connection back to Cameroon. Then wore out his welcome (i.e. they were too poor in to support him and he wasn't employable yet), so he spent years in and out of homelessness, drugs, etc. Went through a one year program in a men's home, got clean, started college, met a bunch of folks that would support him moving forward in life. Relapsed. Recovered. Finished his degree. Got a masters.
My point, not many people have what it takes to do that. It took him from age 18 - 40+ to do so. I have several more examples of US folks going from the worst possible circumstances to success, but as a percentage, those are almost not countable vs the ones that are not able to make that leap. It would be like me asking you why you aren't a billionaire since the US seems to have quite a few. If you are like me, you can't conceive of a path in life that would get you to be a billionaire. If, however, you are a billionaire, I sincerely hope that none of this hit you wrong way and may be we can be best friends?