The aws_iam_policy_attachment resource can only be used once PER policy resource, as the resource manages all of the role attachments for that IAM Policy.
The aws_iam_policy_attachment resource can only be used once PER policy resource, as the resource manages all of the role attachments for that IAM Policy. The best workaround for this issue is to create individual policies for each role attachment that you're wanting to attach.
reference: hashicorp/terraform#11873 (comment)