You are working for a shipping company that is automating the creation of ECS clusters with an Auto Scaling Group using an AWS CloudFormation template that accepts cluster name as its parameters. Initially, you launch the template with input value 'MainCluster', which deployed five instances across two availability zones. The second time, you launch the template with an input value 'SecondCluster'. However, the instances created in the second run were also launched in 'MainCluster' even after specifying a different cluster name. What is the root cause of this issue?