Question

How can I find out who created a project in GCP

Answer 1

You could probably use Stackdriver Cloud Audit logs. 

Filter by Google Project, the very first will be a CreateProject event with an auth principal.

However, this may not be the person advocating for the project. Ownership may have changed hands, or this might be a generic service account.

There is no substitute for project owners claiming what they are responsible for. 

Enforce this by setting a policy that projects without suitable metadata will be shut down and eventually deleted. 

With processes appropriate to your organization, such as requiring all people with project approve authority to confirm they reviewed the list, to archiving one last backup before deletion.