It’s conditional immunity: the Roberts court is openly an instrument of Republican power, but they knew there was a good chance that the Democrats would win an election and so the ruling was carefully crafted to allow them to pick the opposite outcome if a Democrat were accused of abuse of power.
You can see a similar play at work with the unprecedented use of the shadow docket to prevent lower courts from restraining the executive branch without having to take credit for positions which are highly dubious from a constitutional standpoint. If the political tides shift, they can quietly unblock the lower court’s ruling and pretend they hadn’t deliberately given this administration a window of opportunity without creating a permanent precedent empowering a future Democratic administration.
Yup, I really hoped that it might not get this bad, but the Roberts court is basically doing what the Federalist society has been aiming towards for the past 40-50 years, and it's very very sad for all of the US (longterm, this benefits absolutely no-one except autocrats).
You can see a similar play at work with the unprecedented use of the shadow docket to prevent lower courts from restraining the executive branch without having to take credit for positions which are highly dubious from a constitutional standpoint. If the political tides shift, they can quietly unblock the lower court’s ruling and pretend they hadn’t deliberately given this administration a window of opportunity without creating a permanent precedent empowering a future Democratic administration.