Everyone shouting "lock her up" doesn't know exactly what they're "locking her up" for, except for something vaguely relate to emails and the fact they don't like her. Oh, also, they've already decided she's guilty of "emails." Either the FBI says "Clinton is guilty of emails" or the system is rigged.
1. She used her official position as Secretary of State representing the United States to solicit $150M++ of dollars in foreign donations for her personal 501c3.
Imagine how this worked. Picture the scene at a US Embassy social function in some small corrupt country: "Oh sure El Presidente, I'd be happy to look into what's holding up your USAID payments. Sayyy, Bill would love to come and deliver a speech for you. By the way, his going rate is $500,000."
Having our Secretary of State asking foreign dignitaries for payments on-the-side irreparably damages our country's reputation in the world. This is some of the most egregious and blatant corruption we have ever seen in a public official.
3. She made copies of government information, which any reasonable person would agree qualifies as some level of classification, to a personal server in her home that was not authorized to store such information (and as a result the Russians stole it).
2. She conducted government business using an unauthorized private server, and did so specifically for the purpose of concealing her actions and correspondence from both internal and official oversight.
4. She set up some type of shadow internal review process to squash entirely legitimate FOIA requests that might reflect poorly on her department or herself.
Routinely, little people are vigorously prosecuted for far, far less. America explicitly rejects having a double standard for royalty, why shouldn't she be subject to the same rules?