Once a Republican president loses an election or retires after two terms — and is followed by a liberal Democrat — his reputation hits bottom. But once a new Republican president enters office, the prior and now-powerless Republican ex-president is airbrushed into a model of statesmanship to contrast the ogre currently in the White House. Republican presidencies are seen on a downward spiral of always becoming worse — by always redefining formerly despised presidents as at least better than their monstrous successors.
https://www.nationalreview.com/2018/05/george-w-bush-image-rehabilitation-media-strategy-to-disparage-trump/