Clinton has had approval ratings in the 60s and 70s when in in office, both as a senator AND as a secretary of state. Her approval rating right now is a result of the FUD spread by those who've fought her tooth and nail since she said she wasn't going to be baking cookies as a first lady in the White House.
Trump's unfavorable ratings are a result of the kind of crook he is, the stuff he's ACTUALLY done till now in his life, and the shit he's been saying for the last 18 months.
That's all.