Product owner is the one who kickstart the project, he is responsible for documenting Business Proposal or Business Case (this document defines very high level requirements and information of the project); Stakeholder who provides the funds is called Sponsor.
Right now! we have a Project and Funds in hand, next Project Manager joins the project to make the project work on the ground. The extent to which the Project Manager and Product Owners form an effective alliance at this stage, will determine the success or failure potential for the project.
The project manager and the Product Owner must develop a start-up definition that provides the overall context for the project. This definition identifies the information necessary to establish a project. Rigorous definition at this stage makes forward movement more likely in the process of establishing a project.
Project initiation is really two journeys—getting to the project and getting the project started. These really are two distinct steps. The first must necessarily occur at the senior levels of the company. The second happens inside the Project Initiation Phase.
Finally, the relationship between the Project Manager and Product Owner is a partnership. The Product Owner is responsible for creating an environment in which the project can operate successfully. The project manager is responsible for implementing that successful operation.
A well planned project will give results exactly as planned.