Earlier quoted context omitted.
I don't understand how anyone would ever pay. There is nothing guaranteeing you the hackers actually destroy their copy of the data on payment, so they could just come back and ask you for another payment every few months. Or are we really supposed to believe these criminals would follow some sort of made up honor code?
You are completely right, they are criminals there is nothing stopping them from just dumping the data anyway (or launching another attack later down the road). However the hackers also want to get paid, as soon as they go back on their word no one else will ever pay them. But there is another "maybe" to consider (OP did ask for a brief explanation so I didn't go into all possibilities), did they encrypt the data? If…
The hackers are the real victims here