That is how all it started. Were they doing it for fun or money?
Or, it is one of the movies without explaining why they're doing this?
For money, which leads to fun.
It’s a combination of both. The restaurant guy is the one who owns the property, I believe. So he gets some of the money and valuables from the families. And Paddy clearly isn’t a doctor (or has any kind of job). So they rob people to get their bank account money transferred, and they take whatever valuables they have
But at the same time: the restaurant guy remarks to Paddy, “why don’t you just kill them from the start, why do you play with your food.” So Paddy was also just twisted and wanted to have some fun with them