Dynamic blocks and lookp

Terraform
1

Using TF 0.12.20 I am trying to pass along arguments to a custom module where I use dynamic blocks.

      load_balancers = [{
         target_group_arn = data.aws_lb_target_group.syslog.arn
         container_name   = local.container_name
         container_port   = 10514
    }]

In the module I define a balancers variables like:

      variable "load_balancers" {
        type = list(map(any))
        default = []
      }

And my dynamic block looks like:

  dynamic "load_balancer" {
    for_each = var.load_balancers
    content {
      elb_name         = lookup(load_balancer, "elb_name", null)
      target_group_arn = lookup(load_balancer, "target_group_arn", null)
      container_name   = load_balancer.value["container_name"]
      container_port   = load_balancer.value["container_port"]
   }
 }

The issue is with the lookup method. It always return nulle and skip adding target_group_arn or elb_name even if I provide a value into the object I pass along as argument. Any suggestion?