I thought you were in your early twenties. Not an insult or anything, you can even take it as a compliment that you sound young, but am just surprised at your age.

There is a paradox. The people who live in the epicenters of 'diversity' are generally very pro-diversity. This is used as proof that the more 'diversity' you have, the more you like it. There are several explanations offered for this, but most importantly, these people are wildly expensive to live in and they have become not very pleasant places to live in. The vast numbers who fled probably did so because they did not appreciate the 'diversity', and the places known for hosting emigrés from such places are generally bastions of anti-immigration votes. Also, perhaps people who haven't seen their city become a garbage dump might not want it to become one. "These people live in a garbage dump and they don't mind" is not exactly the strongest argument for them.