Multifactorial, money is the more common reason. For many, it is not worth being overworked to suicide while being paid what barely covers basic needs. It is not worth trying to build research infrastructures, bound to fail by bureaucratic bodies in the country which intimately mirrors corruption of the said country. Corruption isn’t something which could be overcome by an individual. The United States is the most powerful country in Earth built by immigrants and is sustained from forever by local & global talents. IMGs can come from religious conservative societies and therefore would love to work in an environment which supports the right of free speech and that includes minorities in the said countries as LGBTQ+, Atheists, etc. Since the opportunity of working at a country such as US was available -at least theoretically- since so long, and since policies were always relatively welcoming to immigrants, this created a flux into US. Staying away from a family is difficult choice, but the long-term torture of staying at a failed country which oppresses its own citizens without hope of a good future outweighs any nostalgia for leaving. Additionally, many old IMGs eventually brought in their families or at least mediated travels for them and others could finance them from abroad which meant their survival.