Not everyone wants to live in a Chinese style mega city.
Fwiw I am a foreigner in Switzerland (I live in Zürich) and I can definitely understand why the people of Switzerland don’t want it more crowded.
Japan's number of tourists has famously exploded over the last decade, and they take trains more than the resident population.
Improvements on various train station (new underground stations in Geneva and Luzern, extra platforms, etc.).
https://company.sbb.ch/en/railway-development/future-rail/na...
(for example, there's also lots of tram, etc. projects)
Japan, Taiwan and China all added dedicated infrastructure which took a long time and cost a fortune (vs the shared tracks currently used for intercity/regional/European freight). Tokyo accepts famously absurd levels of overcrowding during peak hours. Deutsche Bahn in Germany is widely thought of a joke due to chronic underinvestment meaning on-time trains are surprising.
That said, these technical concerns have nothing to do with the 10 million proposal. It's worth asking why a camp that spent decades opposing sustainability legislation has suddenly discovered the word now that it can be pointed at immigration.