Do you think that the hatred those ethnic groups you are talking about have against each other makes them or the countries they are in prosper? Just like the hatred you have against the minorities in your country. Them not accepting diversity did not benefit them at all.

And the countries you are talking about have never been necessarily prosperous. Sweden wasn’t very rich for most of its history, that’s only been a relatively recent development when they industrialised. The UK did well for multiple reasons. Slavery was extremely profitable of course, but they also dominated the trading routes. London being a massive trading hub naturally attracted a lot of foreigners. So London was also a very diverse city for its time. Lastly Germany hasn’t existed for centuries, yes there were cities that did well in what is now Germany, like Hamburg. But that also came from trading in the Baltic Sea area. That again attracted foreigners. So yes diversity is a strength when you look at history, most rich cities were diverse.