Autumn 1991 definitely was when the music landscape in terms of rock changed overnight. Bon Jovi had talked about it in interviews, the recent Scorpions documentary that I saw the other night stated just the same.
That it's not represented in the charts of 1991 doesn't mean too much. You Give Love A Bad Name hadn't reached number 1 until four months after its release, yet Bon Jovi were on their way to superstardom at that point already.
By that time frame, young people seemed to be fed up with those pompous 80's rock stars and that image and the Seattle scene had been creeping up slowly since the late 80's. There was a longing for a change and Richie didn't fit in that time frame, his sound wasn't appealing to people outside a certain niche at all.
That documentary explains quite well how the phenomenon Grunge unfolded when Nevermind ripped up the charts in late 1991.
So it's rather logical that any initial launch the record company had for Richie's album could've been dropped shortly after that.