Me neither! Normal Italian speakers can't decipher it. It is the majority spoken on the island. I had brainstormed some islands and when I researched Sardinia, because I assumed the language was Italian, I was surprised too.
Italy actually has lots of languages, and in fact lots of the population is bilingual, with people speaking languages such as Venetian and Sicilian, along with Italian, despite the fact that these languages are mutually unintelligible; these are considered dialects although they are not Italian.
Well... You picked almost only multilingual islands... it's very confusing. In Great Britain they also speks scots and scottish gaelic, in Ireland they also speak irish, in Java they also speak javanese, in Hispaniola they also speak French creole and French, in Corsica they also speak corsican and italian, in Sardinia they also speak italian, sassarese and gallurese, in Greenland they also speak danish, in Sri Lanka they also speak Tamil...