The hyperbole of the article aside, one needn't be actively and purposefully working for a government or organization to be useful to the same. In this case, the Russians and other illiberal organizations very much appreciate Clinton's response to Gabbard's similar usefulness.

"There is no evidence that Gabbard is coordinating with the Kremlin or with an assortment of foreign dictators and extremists. At the same time, Gabbard has been consistently championed by Syrian dictator Bashar al-Assad’s propaganda machine, an international network of pro-Trump Hindu nationalists, the American far right, and Russian state media. And if some of these forces are trying to use Gabbard as a cat’s-paw, it serves their purposes to cast her as an oppositional force to the so-called deep state, which is exactly what Clinton’s comments did."

I’m a Russian asset. I promote their culture by buying babushka dolls for my wife and listen to Tchaikovsky!