Civil unrest is easy to start. At any one time, in most countries, there is some serious injustice and there are aggrieved people who would like to start a revolution if they just knew how to do it, if they had some financing, and if they were certain of foreign sanctuary should they lose the gamble. They are just waiting for someone to show them or help them a bit. In some places there is terrible oppression on the people and they just take it. They are waiting for direction.
Any foreign ruler can provide it.
There was no historical or ethnic ground for grabbing South Tyrol. Its Austrian inhabitants suffered persecution under Italian Fascism, and after the war, as late as the 1950's Tyroleans died under torture in police custody. In the 1950's a small liberation movement arose there. After a few years it died out. Italian nationalism had mellowed, the European Community was established, and the issue of belonging to Austria or to Italy lost much of its importance.