He played a key role in the Fall of the Sith
The Sith would still be ruling the galaxy to this very day if it wasn’t for the sacrifices of Obi-Wan Kenobi. Not only did he destroy the first Sith to reveal himself in over a thousand years Darth Maul, but he helped train the chosen one, Anakin Skywalker, who would end up bringing balance back to the Force even if it was just for a short period of time.
Obi-Wan taught Anakin Skywalker everything he knew. That made Anakin a great strategist and fighter but watching how Obi-Wan conducted himself and the clear and obvious good that made up his soul had a part in Anakin’s overall redemption.
Let’s not forget Obi-Wan’s biggest contribution to the downfall of the Sith, and that is the watching over and caring for Luke Skywalker. Obi-Wan clearly felt guilty for how he left Anakin burning alive next to a molten lava river. He sacrificed nearly 18 years of his life living in the desolate desert wastelands of Tatooine to atone for that sin.
He made sure Luke was safe, and when the time was right, not so subtly nudged him on the path that lead him to become a Jedi. Not just a Jedi but one who would help his father earn his redemption and also carry on the legacy of the Jedi. Without Obi-Wan, Luke would’ve ended up a grumpy old moisture farmer and Darth Vader would’ve continued to live a tortured life of suffering and internal pain as he controlled the galaxy.