Executive Summary has to be developed **by** business executives (CEO, COO, etc.) using the information provided and prepared by VP/Marketing, VP/Engineering, VP/anything. A project manager of the future project is not involved at this stage. Because the project is not yet authorized and Project Charter is not yet baselined (the PM simply can't start spending resources).
On the other hand, a Project Manager may take a participation in a preliminary/preparation project, which will produce (for example) cost-benefit analysis of the future project, or marketing plan, or preliminary technical solution.
Again, there are **two projects** : 1) create the Executive Summary, 2) implement it.