I don't get it. It's there along with all the other English sources, just sitting there, probably never being clicked on by those logged into D&D Beyond in English. Can it be removed from the English version of D&D Beyond please?

There isn't a version of D&D Beyond Besides this one.  The Manuale del Giacatore was an early experiment in providing a translated version of the PHB here on D&D Beyond sometime over three years ago. 

I don't see D&D Beyond removing it just because you have for reasons unclear have some sort of problem with its existence.  That said with WotC having recently taken to directly producing D&D texts in a number of languages, I suppose this text could be struck from the list because it doesn't match the official WotC release ... or maybe as part of the experiment it's been updated to the current translation so is good to go, and thereby stays.

I like it there and I want it to stay.

D&D Beyond was trying to figure out how to serve non-English language versions of the books. Their first test was the Player's Handbook in Italian and it was easiest for them to gauge interest by making the book a separate source in the menu. For whatever reason (low interest, technical issues, etc) they did not pursue it further at the time. But some number of people must have bought it, so they can't really take it away now until they figure out how to better present the sources.