I was unable to find why I can not display the RowHeader. As a workaround I added an additional column in the data grid to display the sting that I wanted.
...
<DataGrid Grid.Column="0" ItemsSource="{Binding Path=Results}" Margin="5">
<DataGrid.Columns>
<DataGridTextColumn Header="Algorithm"
Binding="{Binding Item1}" />
<DataGridTextColumn Header="LArmAngle"
Binding="{Binding Item2.LArmAngle}" />
<DataGridTextColumn Header="PropellerAngle"
Binding="{Binding Item2.PropellerAngle}" />
</DataGrid.Columns>
</DataGrid>
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