The Cobra Kai season 4 finale sets up a season 5 conflict with Robby Keene (Tanner Buchanan) and his own conscience, which is why he has to leave Cobra Kai’s dojo. Since Sensei Kreese (Martin Kove) will most likely be in jail, this leaves Robby with only Terry Silver (Thomas Ian Griffith) as his mentor, and Silver is making Cobra Kai even more vicious than before. Because of this, Robby is slowly learning that Cobra Kai’s “strike first” mentality is influencing the students around him for the worse.
Aside from the dojo itself changing, Cobra Kai season 4 also significantly altered Robby’s character from bad boy to him realizing he needs to fix his ways. After Robby’s loss in the All-Valley Karate Tournament, as well as his reconciliation with his father Johnny (William Zabka), he has come to terms that much of his life and decisions have been fueled by anger. Cobra Kai season 5 is currently in production, and in order for Robby to change his ways, he needs to break free of the bad influences surrounding him the past few seasons.
At the beginning of Cobra Kai season 4, the new character Kenny (Dallas Dupree Young) is somewhat set up as a reflection of Daniel LaRusso’s (Ralph Macchio) character in the original Karate Kid films. He is bullied furiously by Daniel’s son Anthony (Griffin Santopietro) and is also someone that Robby wants to take under his wing. After Kenny is introduced as Cobra Kai season 4's underdog, his innocence quickly fades. Robby brings him into Cobra Kai, but he soon notices that Terry’s influence is already clouding Kenny’s judgment and Kenny turns into a kid who's angry, mean, and unwilling to forgive. Robby then turns to Johnny for the first time, telling him he knows all his anger has only worsened things. He shares an emotional hug with his dad, setting up a potential relationship between the two for Cobra Kai season 5. Robby finally realizes the hate in his heart is not worth hurting other people, which is why in order to truly grow, he needs to leave the Cobra Kai dojo and its negative influence behind.
Kreese and Terry’s team-up in Cobra Kai season 4 obviously did more harm than good to Cobra Kai’s dojo. After Terry bribed the tournament to have Cobra Kai win, it is now the top, and most dangerous, dojo in the Valley. Robby has already made it clear that Cobra Kai is changing, and not in the way he wants. He knows this is not how he taught Kenny, but also knows that he doesn’t have much control, as he is not the leader of the dojo. To help himself and Kenny, he has to leave to get his bearings and then get Kenny out before the impressionable teen loses himself to Terry Silver's cruel methods. Also, with Tory (Peyton List) knowing that the tournament win was all a lie, a potential team-up for Cobra Kai season 5 can occur with Robby and Tory. Tory can fight against Terry, having her and Robby lead the way of an exodus from Cobra Kai.
The season 4 finale leaves a lot of questions to be answered in the upcoming Cobra Kai season 5. Robby has already had an enormous breakthrough in the season 4 ending; with Terry still in charge of Cobra Kai, their relationship is sure to only worsen in season 5. If there is one thing that Cobra Kai has shown thus far, even the biggest villains can change, and the change is coming for Robby.