Britain's Got Talent judge Piers Morgan told GMTV the attention Boyle received was "crazy" and "nobody could have predicted it".
"She wasn't used to it, and just needs a break," he later told the BBC.
"She said she was exhausted, she said she was physically and mentally drained, she'd been sick a few times in the previous week, hadn't been sleeping, hadn't been eating - and had found the whole weight of the world's media pressure crashing down on her shoulders," he added.
The show's winners, Diversity, said Boyle had been very gracious in defeat, congratulating and joking with them backstage.
"I feel for her because she had a lot of hype around her and she didn't ask for it," the group's choreographer, Ashley Banjo, told ITV1's This Morning.
"She's going to have a great career anyway, and I wish her well in whatever she does. She's a really nice lady."
Fellow contestants Stavros Flatley - aka Demetrious Demetriou and his son Michalakis "Lagi" Andreas - told BBC Radio 5 Live's Victoria Derbyshire show they could sympathise with Boyle's situation.
"It's really, really tiring and even Lagi's not too well this morning so we said that he wasn't going to go to school," said Mr Demetriou.
Boyle found herself the focus of media attention at her home in Scotland
"It's just so draining. They did warn us, they did say to us it's such an adrenaline rush and you got to be really careful the next couple of days after."
Publicist Max Clifford said people in Boyle's situation "need people around them to understand how the business works."
He added that "everyone connected to the show has a responsibility" to help contestants, but its makers - including Simon Cowell - would be aware of this.
Fred O'Neil, one of Boyle's friends who was her voice coach, said it was a "sad situation".
"She just was caught up in all of this and I think that she will never have had an idea, at the beginning, the price that she might have to pay."
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