Why my load balancer doesn't redirect to avaliable ec2 when cpu is 100%?
By default a load balancer will just use a round-robin algorithm to distribute requests evenly across all targets. The load balancer will periodically perform the health check that you have configured to ensure a target can accept requests.
The load balancer does not monitor the CPU usage of the targets. Until the periodic health checks for a target instance fails, the target will continue receiving requests.