Because she's a Clinton and former SOTS. She has the money, power, and influence to get away with it. Well, maybe not so much anymore, though they are trying damn hard to cover her tracks.

If Clinton allowed top secret messages to be sent or received from her private server or personal phone, he asserted, it would be a "deal breaker" for her candidacy for president.

No, it wouldn't, because anybody that would still vote for that lying piece of shit after everything else would do so after this as well.