Yeah, it's because it wasn't even written by the band, but by American R&B producers Jimmy Jam and Terry Lewis, who wrote a lot of hits for Janet Jackson and other black R&B acts. They produced that album for the Human League which came a few years after their other main hits.
Also the original Human League lineup was him and two other dudes doing obscure dorky electronic music. The other guys left the band right before a tour, and the singer just went out to a club, found these two chicks (who were still in high school at the time), recruited them into the band as backup singers, and did the tour. Then they made a #1 album.