By publicly humiliating her in front of millions of people, giving no regard to how she may react. By giving no consideration to how her employment may be affected by their 'joke'.The DJs obviously did not intend for Jacinda to take her own life, nor could even foresee it, but surely must have realised that such a prank could cause deep embarrassment for her and possible disciplinary measures at work?
What? She simply put the call through, hardly world-wide public humiliation. Until she committed suicide, no one even knew her name.
Sadly she was a troubled lady long before this prank call happened, and she had tried to end her life previously. Had she not succeeded this time, I have no doubt she would have tried again in the future - triggered by another even she couldn't cope with.
The actual phone call wasn't malicious, it was quite obviously a prank and I doubt the DJ's had even considered that they'd get put through as far as they did, let alone considered what they would say and do, if they did. Therefore, they didn't have a plan when they did get put through - hence why it went on for as long as it did. In hindsight, yes they should have just put down the phone and not spoken to the staff at that point, but in the heat of the moment, they just didn't think.
I really don't think they should be blamed, and the lady DJ doesn't derserve to lose her livelihood over this - she was only the public part of the production team, plenty of others have managed to avoid blame when they are just as culpable.