After optimizing there are no stats to compare. It only shows information for plan cost and other columns are blank.
Original SQL was only optimizer and alternates found. SQL has not been executed and no run time stats have been collected yet do display and compare.
Please select all or some of the original and alternate SQL to be executed. As they are executed run time stats will be collected and displayed in Optimizer.
Please note, the queries will actually be run by Optimizer on the database, but the process should roll back any changes in the end.