@nimh,
I don't' think that's entirely fair. Two main reasons:
1) I don't know of any leader who, after moving out of the spotlight, didn't see their approval stats go back in a positive direction
2) but the more important aspect here is Trump's unique level of corruption. The financial corruption is obvious but not the key problem or dilemma. That is Trump's unprecedented dishonesty and his attacks (daily) on anyone who challenges him, most particularly, the news media. But it is broader than that because Trump is calling into doubt not merely voices who challenge him but also he calls into doubt any means of establishing truth or facts where he suspects this might cause him damage.
We've never seen anything like this before in US politics and it presents an enormous challenge to news entities - a situation made much worse with the right having built up its own media universe which pretty consistently acts to bolster Trump and his administration. As many media observers (like Jay Rosen) have argued, the combination of the factors I've just noted have confused and neutered most mainstream media. Most people in news media seem to understand quite acutely that Trump is both unique and a real threat to democracy but they haven't yet developed tools or strategies to effectively cope with Trumpism. And obviously, certain habits - the quest for objective and reasoning coverage of divergent views - has driven them far too often to equivalence formulations that make truth/facts more opaque.
One means available to the press (and to us) of properly describing Trumpism is to compare what's going on now with prior GOP administrations/persons. This avoids the problem of Dem versus Republican narratives and biases. That Bush junior benefits from a positive comparison when set against Trump, that is simply inevitable. If someone hits you once with a baseball bat, that's a drag. But if someone else hits you ten times with a baseball bat, the first person doesn't look so bad.
Edit: one final point. The crap we all know about that marked W's administration is moving into history. Bush does not present any current danger to America's left. But all the varied dangers of Trump in the WH are in the present and near future. Trump is the correct target for attention and criticism, where that's due.