Why would Tableau default to a specific filter and/or selection for only one user?

Today, a user experienced an issue where a dashboard in Tableau defaulted to a specific filter selection and a data point on the dashboard was selected when accessing the dashboard. I did not publish the dashboard with this filter selection or that data point selected. This only happened for one user. When other users, including myself, accessed the dashboard, everything was exactly as I had set it when I published the dashboard.

Why was this happening for just one user?

How do I fix it if it happens again? Today, I fixed it by publishing a "new" version of the dashboard.

This could be that the user made a custom view. A user can save their own custom view after making some changes or filtering on the dashboard by clicking this button.

If the user then made it their default in the popup, This would be the view they see when they visit the dashboard again.

Admins can see all custom views for a workbook by navigating to the Custom Views tab from the workbook page. I created 1 to show that it will give you a count of custom views even before clicking the tab.