If you think Trump has done anything constructive, you are not well versed on his history. He is notorious for taking credit for the hard work of others and for finding scapegoats for his own failings.
Obama spent eight years digging America out of a deep, deep economic ditch and putting the country back on a sound foundation. And as is his usual MO, Trump is now coasting on Obama’s hard work and lying his ass off about everything under the sun because that is what the Donald is a phony “reality” TV personality.
As for Obama, his sin was being a black man sitting in the White House. It fired up the nation’s xenophobes like nothing else could. But we all know that. It ain’t a news flash.