^ You say he should not have focused on sales - but you yourself very much do that by measuring his album's worths by their sales numbers. So which one is it?
I think it's simply unrealistic to expect that he would or should have kept selling like Thriller. That was a once in a lifetime - or rather once in history - event whether Michael himself accepted that or not. I really think it was a mistake from him to mention his sales expectations publicly because now even some of his fans keep suggesting that's all he cared about and that is just not true in my opinion.
And why he lost a part of his urban following after Thriller is a lot more complicated than the music and we have already discussed this in another thread. When Bad came out he was very harshly attacked by the media, but those attacks were not really focused on the music but on how he looked. That's when people started to think he was trying to be white and that is more the reason for losing some of his urban following in the US than anything else. And then there is this whole thing with the media playing "build you up, tear you down". After Thriller the "tear you down" phase was on.
And was Quincy doing the same by featuring rap music and contemporary rap stars on his albums and taking in New Jack Swing while producing young stars like Tevin Campbell and others? This is the kind of music Quincy did in 1991:
Music always keeps evolving and it's natural that in 1991 Michael was not doing disco or post-disco music any more, no matter how much fun Off The Wall or Thriller was. And it's not like Michael collaborating with others started with Dangerous. He collaborated with Paul McCartney on Thriller precisely to get white adult contemporary radio play him. Or he had the most popular guitar player at the time Eddie Van Halen play in Beat It. Those moves are not any less calculated than anything he did on Dangerous.
I don't think he "had to" do it in the 90s either. Actually I think these harmed him more than helped him on the long run. In the 80s the game was different - then it was "mysterious Michael". And the Elephant Man and the hyperbaric chamber. If you read his so called manifesto - that was written in 1979 way before Thriller or Bad or leaving Quincy. And that is already a draft of what he will do PR-wise to make himself mysterious. Those are PR tools as well. And those were used at the hight of his success. It's not like he did not do PR stunts in the 80s.
I do not think anything he could do to stop his sales from declining, simply because that's just the natural order of things. After Thriller the only way was down in terms of sales. Then there was the controversy around his looks and then the allegations. Ignoring all these factors affecting his sales will lead you to wrong conclusions IMO.
And how much those hip collaborators defined his music? Dallas Austin or R. Kelly weren't the main features of HIStory. They do not define that album. Teddy Riley was more a feature on the first half of Dangerous, but that was it basically - and like I said Quincy too did New Jack Swing at the time. Everyone in urban music did, so that choice was not unique to Michael. Had he stayed with Quincy they would have still probably done some sort of NJS featuring rap and rap stars and Slash and all. After all that type of thing did was done both on Thriller and Bad as well (Van Halen, Steve Stevens etc.).
The main task of HIStory was not to be radio friendly but to tell "his story". I am pretty sure Michael could have opted to do some catchy, shallow, meaningless pop music and possibly that would have sold more, but that's not what he wanted at the time, but to put his feelings in his music. And I think on Dangerous too. He noticably turned darker already on Dangerous than he was before. And BTW, you still have not answered the question how are the themes and subject matters on Thriller more adult than on Dangerous or HIStory? Because that is the whole point from where this discussion started.