Unable to access more than one element from a list of module output

Terraform
1

I have a nic module and vm module. When i give nic count as 2 and try to access index 0 and 1 of that nic module from vm module it doesn’t work. It doesn’t throw error on plan and apply but it attched only one nic where as two nics were created.

Terraform Version
Terraform v0.12.7
Terraform Configuration Files
# Virtual Machine module main.tf
resource "azurerm_virtual_machine" "vm" {
  count                        = var.vm_instances_count
  name                         = "${var.vm_name}${format(var.count_format, var.count_offset + count.index + 1)}"
  location                     = var.location
  availability_set_id          = var.avset_id
  primary_network_interface_id = var.multi_nic == "true" ? var.primary_nic_id : null
  resource_group_name          = var.resource_group_name
  network_interface_ids        = [element(var.nic, count.index)]
  vm_size                      = var.vm_size
  }

# Virtual Machine module vars.tf
variable "nic" {
  default     = [""]
  description = "Network Interface ID"
}

# environments/dev/main.tf (calling nic module)
module "fw_nic" {
  source               = "../../nic"
  vm_name              = var.fw_vm_name
  location             = var.location
  resource_group_name  = module.resource_group.name
  vm_instances_count   = var.fw_vm_nic_count
  vnet_subnet_id       = module.fw_subnet.subnet_id[0]
  nsg_id               = module.fw_nsg.nsg_id[0]
  lb_enable            = "no"
  enable_ip_forwarding = "true"
}
# environments/dev/vars.tf
variable "fw_vm_nic_count" {
  description = "Firewall VM nic count"
}

# environments/dev/dev.tfvars
fw_vm_nic_count = "2"

# environments/dev/main.tf (calling vm module)
module "fw_vm" {
  source              = "../../virtual_machines"
  vm_name             = var.fw_vm_name
  location            = var.location
  resource_group_name = module.resource_group.name
  vm_instances_count  = var.fw_vm_instances_count
  vm_size             = var.fw_vm_size
  admin_username      = var.fw_vm_admin_username
  admin_password      = var.fw_vm_admin_password
  nic                 = [module.fw_nic.nic_id]
  primary_nic_id      = module.fw_nic.nic_id[0]
  avset_id            = module.fw_avset.id
  disk_size_gb        = var.fw_vm_disk_size_gb
  os_disk_type        = var.fw_vm_os_disk_type
  data_disk_type      = var.fw_vm_data_disk_type
  image_publisher     = var.fw_vm_image_publisher
  image_offer         = var.fw_vm_image_offer
  image_sku           = var.fw_vm_image_sku
  image_version       = var.fw_vm_image_version
  data_disk_enable    = "true
}
```
esource "azurerm_network_interface" "nic" {
  count                     = var.vm_instances_count
  name                      = "${var.vm_name}-nic${format(var.count_format, var.count_offset + count.index + 1)}"
  location                  = var.location
  resource_group_name       = var.resource_group_name
  network_security_group_id = var.nsg_id
  enable_ip_forwarding      = var.enable_ip_forwarding

  ip_configuration {
name                                    = "${var.vm_name}${format(var.count_format, var.count_offset + count.index + 1)}-ipconfig"
subnet_id                               = var.vnet_subnet_id
private_ip_address_allocation           = var.private_ip_address_allocation
load_balancer_backend_address_pools_ids = var.lb_enable == "yes" ? [var.load_balancer_backend_address_pools_ids] : null
  }
}

# NIC Output 
output "nic_id" {
  value = azurerm_network_interface.nic[*].id
}
```