In The Mandalorian season 2, Moff Gideon is in charge of a light cruiser, a ship that’s quite different than the ones typically seen in the Star Wars movies and shows. His ship could easily have been mistaken for a Star Destroyer, a vessel of a similar design. Commonly seen in the original Star Wars trilogy, Star Destroyers are typically captained by high-ranking Imperial officers, and they house an arsenal of weapons along with legions of troops.
The Empire fell as a result of Palpatine’s defeat at the end of Return of the Jedi, but their fall from power wasn’t a total collapse. The Mandalorian season 1 made it clear that many Imperial remnants have remained loyal to the Empire, and are still determined to revive it from the ashes. One of the reasons why these people are still a problem is because not all of their resources were destroyed. Many ships in the Imperial Navy remain in operation. Their leader has fallen, but the Empire still has bases all over the galaxy, just like the one that Mando, Greef Karga, Cara Dune, and the Mythrol attacked in The Mandalorian, season 2, episode 4.
At the end of "The Siege", The Mandalorian showed Moff Gideon aboard a large Imperial ship. Given his position and the size of the ship, some may assume that it’s a Star Destroyer, but it’s actually a light cruiser - specifically, an Arquitens-class light command cruiser. This ship hasn’t made a single appearance in any of the movies but is familiar to some Star Wars fans. It made its debut in the animated series, Star Wars Rebels, which took place prior to A New Hope. These vessels were commanded by some of the villains who battled the main characters on the show. They also appeared in comic books like Doctor Alpha and the video game, Star Wars: Battlefront II.
These light cruisers, which are full of high-powered weapons and support large crews and sizable docking areas, are updated versions of the ones used by the Republic's clone army during the Clone Wars. In fact, they were often commanded by Jedi, like Obi-Wan Kenobi. But during the Empire's reign, the new Arquitens-class light cruisers were typically tasked with patrolling the Outer Rim. This being one of their purposes could have something to do with Moff Gideon’s role in The Mandalorian.
When Carson Teva offered Cara Dune a position with the New Republic, he spoke about trouble brewing in the Outer Rim due to the presence of the Imperial remnants. There have been other references on the show that suggest that the Outer Rim fits into their plans somehow, which lays the foundation for the First Order's origin in the galaxy. As for Moff Gideon’s light cruiser, it could be important in an upcoming episode, especially because of the cargo it’s carrying. Secretly stashed on the vessel is a large gathering of Dark Troopers, which may be key to The Mandalorian season 2. Also, Moff Gideon is now tracking Mando, so the light cruiser may be on the Razor Crest’s tail at some point in the near future.