The things that MC forgets is the arrival of herroine, maybe? I guess at first the public opinion about her will hit rock bottom (not that it will affect my queen lol) and I bet the prince will hate it. So its mission accomplished. But before last the herroine will arrive and make the crown prince fall in love and soon he will fawn over the herroine, asking her for dance, yada, yada, then forget/ intentionally forget to announce the wedding. At last the public opinion for the two of them will hit rock bottom.