While Ahsoka continues to expand the Star Wars galaxy, Star Wars: Rebels laid the foundation for much of what is being explored in Ahsoka. Grand Admiral Thrawn made his first in canon appearance in Rebels and he and his TIE Defenders brought death and destruction to the Rebel Alliance. Yet, despite the success of the Defender, the Empire never got behind the project fully. Instead, the Death Star was funded, and the rest is history. The Empire crumbled and faded into the shadows of history. Yet, there is a strong case to be made that the outcome would have been different if the Empire hadn't made one critical error.
Source：https://www.cbr.com/star-wars-rebels-proves-the-empires-biggest-mistake/
