> Presuming we are talking about migration, most of these source countries were able to fight and win European colonization in the past, why do you think that's easier than fighting corruption?

While I neither claimed "nothing can change" corruption nor that fighting corruption is more difficult than fighting European colonization, here are some arguments to your straw man:

Corruption is very insidious to combat because you don't have a clearly demarcated enemy to unite against. Corruption spreads through all layers of society and most people in deeply corrupt societies will be both victims and beneficiaries of corruption: you want your house built and saved up enough dough? Sure you grease the wheels a bit so you can start building right away. Also, your brother who's helping you finance the house is a civil servant and a good chunk of his income is a result of taking bribes. The government itself sees it as "tips" that justify lower wages, and you sure as shit don't want taxes to go up with all the baksheesh you need to hand out...

At best you're in a "glass house" scenarios, it's very difficult to break out of without a general amnesty and serious external pressure, because all the parties that are actually qualified to run a government (or similar corrupt organization) are implicated.

Yes, and the founding belief of corruption is that, "that's the way it works", "everybody does it", "this can never change".

That essentialism is exactly the notion the poster I was replying to was echoing

Western countries were also corrupt at a time, bribery was common, yet things can change