As much as the ghost groom did not want to marry a stranger and claim a wife after his death, the other party no longer had any other choice.
The old couple's act of enclosing his desire in the red pouch and incorporating it to start a spirit wedding was as good as tying him down to the mortal realm as well.
Unless the spirit marriage took place, the ghost groom would not be able to cross his afterlife anymore even if he wanted to.
His final wish before he died was to get married. Yet before his last wish could even get fulfilled, his life already expired.
This became his unfinished business and that was why he failed to cross the afterlife and became a ghost instead who roamed the mortal world, in hopes that he would someday fulfill his desire one way or another.
However, he did not expect that someone would be as sick in the head as to force a living bride into marrying a ghost groom like him.