Meh. It's trashing someone who doesn't have the bully pulpit to defend himself, and happens in lots of aspects of life.
Blaming the predecessor goes back thousands of years. God forbid one die. Then he gets blamed for everything, including world hunger, lack of world peace, lack of a cure for cancer, the weather, climate change, the fact that pretty much everything costs something, etc., etc.
The OFC will remember that when Bill Casey (then Director of the CIA) died in office, he became the lightning rod for not only the whole Iran Contra scandal, but also everything wrong in every branch of government in all of Washington.
Every President except George Washington has done it. And the only reason Washington didn't was that, being first, he had no predecessor.
The concept is equally prevalent in the workplace. When someone leaves a company, especially a big one, you'd think the poor guy single-handedly tanked the whole enterprise with laziness and incompetence.
This is not new and won't end when Trump is gone. Or his successor. Or his successor's successor, etc., etc. ad infinitum.