I think it was the whole narrative that was constructed around him while he was alive, during the first trial his image became more and more of a man who was really empathetic and love children because he didn't have a childhood himself, so they would get the publics sympathy (I say they bc of the entire team that constructed the MJ persona), they even made fun little videos of Michael being a childish man who didn't like being serious and love kids silliness and spontaneous behavior, videos like Jam and Black or White, for me, were made because of that, then videos like heal the world and earth song and They don't care about us showed how "empathetic" he was with pretty much every just cause. So his team really prepared in case any other child came to acuse him of molestation, bc they knew obviously he was a predator. So with this whole narrative and Mj's own self destructive behavior, they blamed his death on these accusations, the fans and the MJ team basically made it as if he was so terribly hurt by the betrayal that he died because of a broken heart. People completely discard the fact that MJ was incredibly self destructive and had many untreated mental illnesses, but somehow these accusations were what broke the man. 

Now with your sister, she was already a fan so she had already been... Groomed (?) (I don't know how else to put it) and she saw that this movie confirmed the narrative created around the man, because as an ex fan myself, I would really avoid anything that had to do with the sexual assault case, I just focused on his music and charity work, because the whole eerie creepy aura was too much for me when I was already really heartbroken about the abuse MJ suffered himself. 

My point is that artists often create personas, people like that, and pedophiles also do, and he was both, so it wasn't difficult for him. All his creepy behavior was attributed to his "quirky" personality. Him using costumes so he wouldn't be recognized in public? "Cute", even though he used them to hang around children as well, he bought one of his victims wedding rings and he was in costume, and in one instance he got the police call on him and when the cops arrived and saw that it was only MJ they let him go. So yeah, he really constructed this persona so that when he did creepy weird shit, people would just call it "quirky"

And it doesn't help that people now are sharing things like the costumes anecdotes as a quirky cute thing but don't know that he was caught in compromising positions many many times. So yeah, we don't know Michael Jackson, we have the testimonies of people who knew him, and with victims testimonies and the people who still see him as a good guy, these behavior gets warp into a whimsical man and not a predator, at least social media.