An Insights User security role is automatically assigned to all users as part of the Sales Intelligence installation process.
The ISV Extensions privilege is assigned to all users to enable them to view and use the Navigation buttons in the Insights Summary panel, which is the standard customization for the Account, Contact, Lead, and Opportunity entity. If this privilege is not assigned, users will not be able to navigate from Summary to Detailed panel. See Getting to Sales Intelligence in Microsoft Dynamics 365 for more information.