Why do Austrians speak German?

Many Swiss consider standard German - or to be more precise: Swiss Standard German- a foreign language. They switch back and forth between dialect (and there exist more than just one variety of dialect in Switzerland). The switch is very noticeable when you listen carefully, even if you don’t understand neither standard German, nor Swiss dialect. When the Swiss speak standard German, they also tend to speak slowly which is a big help if German isn’t your first language. Feigning / mocking a Swiss accent in Germany always involves speaking exaggeratedly slowly.

The distinction between standard German and Swiss-German dialect causes a problems for Swiss citizens from the French or Italian-speaking parts of Switzerland. They learned standard German in school, but when they want to bond with their fellow countrymen in the German-speaking part of Switzerland by talking to them in (standard) German, they find out that this isn’t actually the “real” local vernacular.

The difference between the dialects in Austria and Austrian Standard German isn’t nearly as distinct which makes it more difficult for foreigners.

“C”, eh? “N”, eh?, “D”, eh?

That is correct. “High” in this sense can be interpreted as “Highlander” - the dialects that underwent the most sound changes were the ones spoken in the mountains.

Note that there was a previous Germanic sound change known as Grimm’s law that all of the Germanic languages, including Dutch, English, and the Scandinavian languages, went through. For the foot example above, the Proto-Indo-European or at least Proto-Centum form looked something like “pod”, and Grimm’s law changed the p->f and d->t, producing “foot” in the Proto-Germanic languages. English and Low German kept that arrangement, while High German changed it to “fuss”.

By contrast, the Italic/Romance and the Celtic languages did not undergo any of these changes, so they often have a word that is closer to the root, such as Latin’s “pedis” for foot.

With some sleight of hand, it is.
But it suits everyone to ignore the details: Sardinian and Sicialian are certainly Romance languages, but they are not Italian. Italo-Dalmatian languages

For instance: La vidisti chissa cucujara? n’antri tanti duppiji haju mu ci mandu. Mi lu saluti e statti bonu. From La Calabria 2:2, 10/15/1889, p. 16.

You can’t argue that it’s Italian by either grammar or vocabulary. I think an Italian speaker would have no problem with the last sentence, but would probably struggle to read the first one. (This is from one of the dialects of Calabrian which is linguistically Sicilian.)