Infrastructure Projects concerning common issues such as Kavery Water dispute etc shall be handled by Central Government. Alternatively TN and KN Government can jointly develop the project with some give and take.
The problem is that people in KN have a strong and hard feelings when it comes to Kavery water. This is called Ground Reality. In a democratic system, No politician an afford to ignore people's feelings. So there is really no point in blaming KN politicians.
TN and Karuna is fully aware of the ground reality. They are aware that a large population of Tamils reside in KN. Still they go ahead unilaterally to rattle an old dispute and put so many of their state people in trouble.
The blame is squarely on TN Government and arrogant Karuna.