It is easy to get lost in all the details when building the future. The end game is utopian and complete. The resources you have to build it are however limited.
By keeping the scope small:
You prevent over-committing.
You prevent being occupied for a long time before you can show results.
Everybody at the table can understand what is going on here.
It provides a foundation upon which to build the following step.
It provides value sooner, which assures your stakeholders.
It verifies your initial assumptions, reinforcing your roadmap. Or arguing for an earlier pivot, preventing a costly pivot at a much later stage.
Rome was not built in a day. End Game configurations are not meant to be about grinding a long single sprint. To me, that is one of the powerful aspects of applying Scrum in your innovation projects. Many small, controlled steps, leading to big results.