Its capability to manage not just Cloud platform but other aspects of Infra team like DBA, Storage, Security, and tools like Kubernetes, VCS, and list is never ending. I majorly use it for GCP/Oracle/Rancher/MySQL/AWS/Azure/Kubernetes/GitLab to name few.
Cloud agnostic approach (you can't reuse most of the code - resources are provider-specific, but you can use Terraform for interactions with various clouds), automation, modules re-usability, infrastructure as a code approach.