As you said, it's not about ideology, it's about influence. And Russia is trying its best to increase its influence in Europe (and also other parts of the world), and if Trump gets elected they likely will gain much more influence (given he really stops supporting Ukraine, weakens NATO support, doesn't care if Russia continues taking other "unimportant" countries. All those things are things that he promised his voters.)

If too many people ignore Russian's spreading influence they'll only be forced to stop ignoring it when it's too late and they've set up a few more puppet states already.