The job description for Checo's seat is to be Max's support driver. RBR are looking for a driver that will follow team orders and consistently finish high enough in the points to guarantee them the constructors championship. Someone "good enough" that will systematically accept to give Max priority.

Tsunoda is an excellent driver that consistently performs exceptionally well and would certainly do much better than Checo, but his anger issues on the team radio over the last 3-4 years and what happened in Bahrain this year probably really hurt his chances for a seat at RBR. He's just not building the right CV for the job.

Helmut Marko called Tsunoda their "problem child" a while back because he couldn't keep his emotions in check. That's probably how he's still perceived internally at RB today with his continued outbursts.