If there is one thing that Star Wars fans can actually agree on, it's how much they love Obi-Wan Kenobi. When news broke that Lucasfilm was developing an Obi-Wan series for Disney+, with Ewan McGregor reprising his role from the prequels, franchise devotees were ecstatic with the prospect of seeing the Jedi Master back on screen. The series will take place between Star Wars: Revenge of the Sith and Star Wars: A New Hope, and follow Obi-Wan in exile on Tatooine while guarding a young Luke Skywalker.
Details about the upcoming project has been scarce, but one thing was confirmed by McGregor: The series will be only one season of presumably four episodes. While many fans were disappointed that they will only get to see McGregor in the Star Wars universe again for a short time, this move might actually be a good thing.
The story of Obi-Wan Kenobi has been told numerous times across both the original and prequel trilogies, Star Wars: The Clone Wars and even briefly in Star Wars Rebels. There are also several comics and books that feature or mention Obi-Wan in some capacity. Clearly, much of Obi-Wan's life has already been explored, especially in print media that offered glimpses into the time period that the series is set to take place in. Since we already know how his story ends, there is no need for a multi-season story that doesn't add anything new to Obi-Wan's legacy.
By only having one season, the Obi-Wan series can focus on telling a complete story that is actually worth telling rather than just filling in a perceived gap in the Star Wars canon. Similar to Rogue One: A Star Wars Story, the series can touch on an obscure part of Star Wars history that leads into the main series while also standing on its own. In Obi-Wan's case, the series could lead into the moment that Obi-Wan stumbles upon Luke in the desert in A New Hope.
A single season story will also help the series avoid becoming self-indulgent, which is something that the Expanded Universe (now called Legends) suffered from during its run. In 1978, Lucasfilm and its licensees created a cottage industry out of telling side stories about central characters, and exploring the lives of (ultimately meaningless) peripheral figures. While there are some genuinely great Legends material, such as The New Jedi Order series and Star Wars: Knights of the Old Republic, the majority of Legends content is mostly superficial when it comes to the main series, and at times even contradicts the films and leads to retcons. So much Legends content was produced over its 30+ year run that a majority of it tends to get lost in the shuffle.
An Obi-Wan series that goes on longer than it should runs the risk of adding too much to the already expansive universe and contradicting a series that is already infamous for its numerous retcons, as well as losing good will from fans if the series goes on for too long and goes down in quality. The Star Wars community is already heavily divided about Disney's numerous changes to the lore and questionable decision making. The last thing Disney and Lucasfilm need is to squander even more good will with their Obi-Wan series by self-indulging and putting out more than is needed.