It’s a rule of thumb not to put your Queen under fire too early, as you can see from this position my Queen was on b6 by move 7 but came under fire from a Knight on a4. In the Caro-Khann I think this rule has an exception, the Queen on b6 generally supports the pawn on c5 which is normally pushed c6-c5 (looking to break in the center or have White capture and Black’s dark squared Bishop recapture) and also keeps an eye on b2 tying the White Bishop to the defense of it until b3 is pushed or some other defense comes around.
The Queen is relatively safe unless White deploys extra effort to attack the Queen, which wastes time and disrupts position and development. The Queen is mobile enough to avoid these attacks and strong enough to counter attack in response. The main fall of the game for White was the extension of the White Knights in order to attack the Queen and overlooking a central double attack. If White had spent time developing and castling the Queen could never infiltrate and wreak the havoc she did.