@Fagato
I think because Johannes is powerful enough to override a maid’s words, he just let it slide.
Also, emperor needs to marry her because she was the princess of the land he conquered, and during wartime, she was regaled as a hero after helping many. They hold her in high respect, and by marrying her, will subdue some of the unrest you get after conquering some land. I think a earlier chapter just focuses on this.