If Italy as a whole would be more economically successful then maybe a bigger share of German speaking voters would likely vote for the Italian parties.
Lolno. (There wouldn't be an SVP today if that had been true in the 50s and 60s, just for starters.)
There are some quite different reasons to the South Tyroleans being very hostile to the Italian state in the 50ties and 60ties, which had nothing to do with economic reasons, and everything to do with South Tyrol being run from Trentino by the Italian majority, 2 decades of persecution under the kingdom and fascism, the Italian still being dominated by the first generation settlers and South Tyrol lacking any autonomy in general.