Most will say that the victims were gullible. My opinion is that they were brave. Their moves to report helped others from ending with the same fate.
The perpetrator struck by providing very narrow time window for his victims to response. Most of his victims were under distress at the time and whatever decision they made was of poor judgement. That's how con-men normally operate. In this case, the perpetrator was also a rapist. Unfortunately, he (Mani Velmurugan , 28) was not charged and convicted of the crime, except for a conviction on criminal intimidation (sentenced to 32 months behind bar). To me, a rape is when victims didn't have a choice and the "consented sex" was under duress. But legally, it's difficult to determine this type of rape. It's not like statutory rape in which by clear definition, the act is punishable.
The next question is why would victims still be unaware of the risk of sextortion? Were they unaware of the technological capability of webcams to record (and not just for real time viewing)? Did they think that they have found their trustworthy soul mates (and hence sending compromising pictures of themselves was safe)? But how could you be sure without even meeting the person in flesh? I hope public awareness on this subject will help highlight this risk.
One thing we need to bear in mind, the victims were given very narrow time window to act. Victims acted under extreme duress. The prospective damages to the victims were usually too great that they would be willing to do anything.
One thing we have learnt, the more the victims give in and suffer in silence, the more the motivation for this crime to thrive. When a crime idea works, it will be copied and used extensively. However, when victims start reporting to the police and the action is translated to convictions (as well as providing the public an awareness of such crime), they helped to prevent the crime. I respect that.
Update: Mani Velmurugan was not charged with rape because his victims did not file them. Would they have succeeded in getting justice if they did? "Consented sex" under duress is no consent.