A different kind of admiral
Thrawn comes from outside Imperial space, from the Chiss people, and climbed the Imperial ranks on pure tactical talent. When the rebels of the Ghost start causing too much trouble, he shows up in the Rebels season 3 premiere as a Grand Admiral, tasked with wiping them out.
His method stands out right away. Instead of sending more ships, Thrawn studies the art of every culture he faces. He believes understanding what a people creates reveals how they think and where they're weak.
Commanding the Star Destroyer Chimaera, he works alongside Governor Arihnda Pryce and Agent Kallus. He speaks softly, gives praise when he thinks it's earned and almost never loses his cool. The rebels quickly learn this makes him more dangerous than any shouting officer.