The Ahsoka series is, essentially, a Rebels sequel

The Ahsoka series’s trailers are jam-packed with characters from Rebels, and the general conceit (Thrawn is trying to return to power, and Ahsoka, Hera, and Sabine need to stop it) feels like it picks up right where Rebels left off. The final scene in Rebels (which finished airing back in 2018), took place after a time jump—Ezra had been missing for years (him and Thrawn disappeared at the same time), Sabine was living on his home planet Lothal, and Ahsoka arrived to pick Sabine up so they could go search for Ezra together.
With Ezra and Thrawn both trying to return to their respective fights, we’re in a natural narrative place for Ahsoka to pick up and continue those threads.