Event sourcing is used when a business analist edits the application model, and when an end user edits the end user data.
When you edit the application model, you can group events together as a branch, and apply the events from a branch to another branch to merge them. When you have a separate Development, Test, Acceptance and Production environment, you can apply a group of events (that were created in one environment) to another environment, thus letting them flow up or down through your DTAP street.
The user interface screens can be created and edited while running the application, giving a true WYSIWYG experience.
This mechanism can also enable each user of your (web) application to tune his or her personal user interface experience, e.g. by dragging and dropping fields. Each such a change is stored as an event, and (re)applied when necessary to the end user's copy of the application.
The technical details of an ESRAD architecture include decisions like which (parts of) events are statically typed or dynamically typed, do dynamically typed elements refer to an instance of a meta model, etcetera. These kind of design decisions, and many others, are elaborated in the book Event Sourced Rapid Application Development, which is a deliverable of this research project.