This sounds more like the natural progression of life and would in large part have to do with the kids getting their own lives and other interests once they grew older, not so much MJ stopped calling because they got older. As kids they went to Neverland to jump up and down on bouncy castles and have fun. But teenagers won't be prioritising petting llamas, and MJ isn't going to help them write a CV to get a corporate job when they turned 20.
I doubt he was ever a best friend to any of these kids, I think that as adults they exaggerate their childhood connection to MJ for obvious reasons. By some accounts he was hardly ever there when sleepovers were happening and it was just kids running amok in his house. I think MJ found a safety blanket in having kids around and nothing more (which is also wrong, because kids are not supposed to be parenting some adult stranger).
How exactly does this constitute abuse, exactly? Are all of the people you made as friends in your youth still your friends today? What made MJ any different, people may not be friends forever, that's normal life. So because one is a celebrity it means that you have to keep the friends you've made when you were young and dropping them is abusive, that's dumb.
Michael Jackson was a regular dude, who dressed in jeans and, shirts and slacks, a businessman... MJ KoP was an alter ego for the stage, he dressed flamboyantly, was aligned to Neverland; although he didn't stay there much, that's not who the real Michael was. MJ KoP was a character.
How was he ruthless in business more than anyone else in that industry? He was a businessman who, at least in his younger days, before he was overcome by prescription drugs, other physical and medical ailments including what seemed to be depression (my opinion), he did exactly what Paul did, by music catalogues which includes music by various artistes. Paul was given first dibs in purchasing the catalogue and he refused, MJ did not, he, by the way, had to fight others who were willing to pay the price for it and he did in 1985. Paul lost out too damn bad...