So what you are saying is that these places have not built enough housing. That sounds like the actual problem, not the population size.
I support YIMBYism for ones own countrymen but I don't see the need to fit as many people as possible in your country. A Switzerland with 25 million people will be a worse place to live regardless of whether the housing supply keeps up
That doesn't explain everything, obviously, but I think you need to take it into consideration. For decades I've heard this in some form from people: "Oregon is amazing, but I had to leave when I couldn't get a job." Meanwhile the Sea-Tac region has had amazing growth, packed wall-to-wall with a range of companies.