For example: When a message arrives in an e-mail requesting the private key, many beginners will respond to this message and send their key, which is really sad.
I have seen a lot of people falling into a trap like this. Seen them on different social media.
Most likely they have been social engineered by those scammers. Obviously it is the fault for the victim.
Should always be careful, double check if the link is unsuspicious and safe.
Just to ask, can someone be hacked if he answered a call from an unknown number? Is there any malware that's able to have access on your phone by answering phonecalls?