Having followed a number of these kind of trials - I've listed a few examples below - it's really not getting together because you share an interest in torture. It's usually something that develops over time.
There is always a ringleader, a group of followers and there is usually a girl at the heart of it - either it's happening because of her and/or she's right there stoking the fire. The ringleader will normally start it - maybe with a slap or a punch and instead of being horrified, like a normal, decent person, the followers will, over time, join in because they find it amusing and/or they're scared of the ringleader turning on them. There then almost becomes a competition to think up more ways to punish their victim with escalating cruelty, violence and sadism.
The victim is usually vulnerable in some way and desperate to make friends. I've seen it mentioned that Shakira was vulnerable and there was possibly a learning difficulty - this would make sense as to how she became so enmeshed with the people who eventually killed her. I hope this will be explored and covered in the sentencing remarks because I want to understand it.
And it pretty much always involves people who are the absolute dregs of society - uneducated, unemployed bottom feeders with nothing better to do with their time than make someone else's life an absolute misery and get off on it. Drugs and/or alcohol play a big part in their day to days living. They take control of the victim, get access to their money in some way and effectively turn them into a slave.
Michael Gilbert, Luton - learning disability
James "Jimmy" Prout, Percy Main - learning disability
Lee Irving, Newcastle upon Tyne - learning disability
Gemma Hayter, Rugby - learning disability
Steven Hoskin, St Austell - learning disability
Jamie Dack, Southampton - slightly different as he was classed as vulnerable due to being completely out of his depth in the homeless community but it's still horrific torture by a gang which escalated because of a girl