The Russians exerted a vast amount of effort to recruit and generate sympathetic leaders in Europe (and elsewhere; i.e. Trump). They had a lot of sympathizers in Germany, and a small cadre of NATO-skeptics in France.

Austria is a lot smaller and easy to influence.

It's also not in NATO, and there is strong public sentiment to stay out of NATO -- which means there is a vacuum Russia can enter in ways that it cannot with full-on NATO members.