If one understands the characters of Virat and Sai, then it will be easy to see why things happens this way.
These are not us who are in the story. These are the characters with some ingrained traits. Just like someone who cant quit smoking knowing that it might kill them. Each character has similar weeknesses and strengths that make them unique. These traits of them will only make the story interesting. If all are perfect, then where will be the story?.
Just saying