I dunno. (I don't watch Strictly or follow slebs, just reading posts & links.) We're just average internet insomniacs here, and we all know that a dance bootcamp to professional standards is going to be brutal. Showbiz bods are at least as likely to know as we are - plus they have access to dancers, previous Strictly contestants, and probably the show's team.
They can't not have known what they were committing to. For that, they were getting massive exposure, a paycheck and a super-toned physique for a while. I can see that they might have talked themselves into it for the benefits, preferring to ignore the real difficulties involved ... and then been mightily shocked when the reality turned out to be as hard as they knew it would be.
I think they're wrong to throw accusations around, though. Nobody can gently coax a non-dancer to show standard in a few weeks, they'll have to push and keep pushing. Unless the professionals were actually beating them up or yelling targeted insults at them, they were doing their job. Which was to make a few pampered celebs train very, very hard.
If the contestants couldn't stand it, they should have come out and said "I can't hack it, sorry" instead of claiming psychiatric injury. They might have sacrificed some of the career benefits by dropping out, but the public would've treated them sympathetically and they'd probably get lots of interviews.