Since implementing T222292: Add search box for choosing categories to include in the Campaign settings, the Update Campaign page no longer shows you which categories you have selected already.
As soon as the user lands on the Update Campaign page, we need to convert the JSON category data that has been served into the actual selections in the UI.
We simply recreate all the rows, exactly as we do when selecting a single category from search box - T224325: Generate selected category HTML from search select on Create/Update campaign page