They're saying these are CAATSA sanctions. At least in part.
The legislation called CAATSA didn't say, "Do this, this, and this!." It said, "This is what you can do if and when you find cause." The admin didn't do it on the first day that the law said they could; they did it a couple of months later, so I guess any cause-and-effect connection was backgrounded. Many understood the law from the way it was presented in just their version of the media to be a mandatory imposition of sanctions. The text of the law doesn't even allow that as an inference, so either the media misrepresented the law or the media were misread. The fakeness of fake news is sometimes provider-side, but sometimes it's consumer-side.
Could the administration do more? Most assuredly. Could they rescind even these sanctions? Sure.
Will the sanctions have the desired effect?
Not in the least. Action taken mostly out of anger, a desire to do something, and possibly to get revenge very seldom proves all that useful; moreover, the timing couldn't be much better. "Look, Russians, we're hated and need to stick together" is a reasonable sort of agitprop piece. The Kremlin's concern isn't Putin's winning, but turnout. They have a big legitimizing GOTV campaign going on now. It's hard to claim a mandate with a 0.5% majority, it's hard to claim a mandate with 25% of the electorate. Not that politicians don't (just look at the Catalan independence referendum, for instance).
The CAATSA was apparently mostly feel-good legislation, but obviously didn't even accomplish that.