The Republicans have been attacking her for just about a quarter century because they don’t like her husband. This cycle, Bernie’s supporters piled on from the left. It’s pretty much that simple.
Clinton is very popular when she’s in office, and largely unpopular when she’s running for office, which might suggest that she’s better at doing the jobs than she is at being a politician. Weird that that’s exactly what people claim to want and yet when they get it, they whine that she’s (1) not pure enough, or (2) just as big a liar as Donald Trump. It’s… frustrating to watch.