Al Capone was the most famous person in America, and everyone knew he was a gangster. They had to get him on tax evasion. The problem isn't knowing who the gang

Al Capone was the most famous person in America, and everyone knew he was a gangster. They had to get him on tax evasion. The problem isn't knowing who the gangsters are, it's bringing an air-tight case through enough incriminating evidence that can be used to convict. That is different than staying under the radar, which is why I put that as a different paragraph. The government knew what they were doing, and were building a case, because you could see something was going on. If you're using encrypted messaging, they can see that something is going on.