Because that's what he did? Because that was his content? Because that's what piqued the interest of the newspapers in the first place?
Or are you suggesting the government in fact asked the Times to investigate it and discover his name?
Not neseceraly, but there wasn't really any good reason that I can see for the police to shut him down, unless their superiors deemed it nesecary. And if you follow the command chain up you end up with the government as the most superior of their superiors...
So they may not have had him uncovered but they undoubtedly took advantage of it once it had happened.