[palmer]

By saying its a Russian rumor, or that the Russians believe it, Brennan decoupled it from a direct affirmative statement that Hillary initiated it

Then why make any statement? Why not just do the spying and shut up?

[Pearls Before Swine]

Because by making it a supposed external threat, you can justify expanding the government counterintelligence effort. FBI, release planted news stories, share rumors among man agencies so they will be leaked as if they are vetted intelligence, for example.