In the early days of the internet, people found ways to share music files with others for free. People had a good time getting free music until suddenly the platforms that allowed this to happen shut down. The issue with sharing music is that it violates intellectual property laws. Federal authorities stepped in and closed platforms that allowed music piracy.
The same thing happened when people started to share movies, television shows and video games. Any creative work such as these typically has a copyright, which means that only the person who owns the copyright can distribute the material. Such piracy is in direct violation of copyright laws. The government held those running the platforms accountable, and in some cases, if you had used the platforms, you also faced charges.
The FBI explains that digital technology makes it very easy to share copyrighted materials with others. Especially in the beginning, those who owned music copyrights were not prepared for the potential of piracy. Today, though, most creators have processes in place to prevent this from happening.
However, at the time, piracy of music led to an extreme loss of income. You did not have to buy the music when you could easily download it for free.
Since the industry today has a fairly strong system in place to prevent music piracy, it is not as big of a problem at least in the U.S. Most music piracy occurs overseas. The focus of the FBI is now on trade secret theft and product infringement, which typically happens in conjunction with counterfeiting and scams.