There's also apparently this view in the industry, as said by a Head of Comic Adaptation department at Kadokawa in an interview:
Men tend to like the set up of one hero with a lot of heroines, whereas I get the impression that women like for the love interest to be set in stone and for the process of how they got together to be depicted in great detail, even if there are a lot of attractive men in the story. This doesn't just apply to iseikai. Men's and women's comedic romance follows similar trends...
When there is one set love interest, the main couple may get together early or late, but when there are multiple love interests, it's pretty much guaranteed that the MC won't get together with anyone for a long time to keep the status quo going. Whether that view on (Japanese) men's preference is justified or not, who knows? They could be making that conclusion based on sales figures.