They've had 65 different governments since WW2. Basically, the states and regions have authority to spend national tax dollars and Rome has almost no control. Regions hold the Italian government hostage as a normal course of affairs. The federal government is extremely weak, and as a result Italy has a gridlocked government that makes our deadlocks in the U.S. pale by comparison. Most of this is the result of an overreaction after Mussolini and WW2. The result is a deadlocked government and high levels of corruption. The reforms attempt to address those issues.
The problem is that this referendum is pretty badly written. The reforms attempt to bring Italy more toward European parliamentary norms, but I don't think it really accomplishes that goal. It's unecessarily complicated, and removes power from the Senate. Since most people don;t understand the reforms, the vote has pretty much been a vote of confidence on the current PM.
This article isn;t bad. The Economist has some good stuff on the vote as well.
https://www.theguardian.com/world/2016/nov/30/italy-referendum-all-you-need-to-know-about-renzis-crunch-vote