The criminal intent part is the FBI's job, and will likely apply, at the very least, to things like Clinton's attempt to delete thousands of messages before handing over the server (messages the FBI was able to obtain anyway due to offsite backups, going by the extrapolations observed and detailed on http://www.thompsontimeline.com/).

Even if she's not found guilty of violating any major law, this kind of obstruction of justice alone is in a class of behavior we impeached her husband over. I imagine the FBI doesn't take kindly to the people they're investigating putting the bureau through hassles like this.

I guess we have different definitions of "likely" since the only reasons given are:

(1) Clinton and her aides have insisted that she didn't. They say none of her emails included material that was marked as classified at the time.

(2) She says she didn't, and there's no known evidence that she did.

(3) "If all she was doing was exchanging emails with her staff, I don't think they can prove that she had the intent to retain anything," a former top government lawyer told me.

Like I said, those are hardly unbiased or definitive assessments. Clinton and her aides have every reason to say that there was no wrongdoing. The government lawyer quoted even says "If" acknowledging that it is an assumption. As for the IG report, if it had said the violation was minor and mostly because of regulations implemented only after she left office, which had been claimed before, then it would be looking really good for her. As it stands, there is still an FBI investigation looming.