A great-grandparent or even a great-great grandparent from Italy used to be all it took to guarantee Italian citizenship. A surprise decree has now changed all that, making it much harder for those with Italian ancestry to use blood line as a pathway to become Italian.
On March 28, the Italian government tightened regulations for claiming citizenship by jus sanguinis, or descendent blood line, effective immediately.
Basically you now need an Italian parent or a grandparent who was born in Italy, or an Italian parent who lived in Italy for at least two years before you were born, to be eligible. This is a major change to the citizenship law, and caught everyone by surprise.
From reading other news reports it seems like this was pushed through because not enough folks were actually establishing a connection to Italy and just trying to get into the EU. Remember that one of the changes is that if you have the Italian passport today, but you were not born in Italy, you can still pass it on to your children - you just have to live in Italy for two years first.
According to https://www.studiolegalemetta.com/press/italian-citizenship-jure-sanguinis-restrictions/ they’re also planning to require spouses to live in Italy for two years before allowing them to naturalize (currently a spouse who lives abroad can naturalize regardless of where the couple lives).
And another planned change is to allow minor children of Italian citizens to naturalize after living in Italy for two years.
Rightly or wrongly, the basic theme seems to be that they’re trying to push more folks who want the Italian passport to actually move to Italy.