The First War and the wizarding underworld
I'm in the process of writing a fic set during the First War in which the main character is known as Knockturn Alley's number one go-to wizard. Much of the story centers around his struggle to determine how far he is willing to support Voldemort, but much of it is also intended to depict the war itself and the evolution of Voldemort's grip over wizarding society throughout the 1970s.
It has made me wonder about the relationship between Death Eaters/other Dark wizards and the rest of the wizarding criminal underworld. The books clearly show a difference, in that there are some crooks like Mundungnus or Aberforth who have no interest in Dark magic or Muggle domination. In other cases, the lines are more blurred.
So my question is this - what sort of effect do you think the growth of Voldemort's power and influence would have had on the criminal underworld of wizarding Britain throughout the 1970s? In DH, Aberforth mentions trafficking potions and the like through his pub. Would this sort of illegal trafficking increase during the First War? In what sorts of things? What other changes might take place in this underworld? Do you think everyday crooks would be more or less inclined to support Voldemort or do you think it would make no difference whether they're a crook or not?
I'm looking to set the stage on which my fic stands, so any and all comments are welcome! Note that my fic follows the entirely of the 1970s, not just the end of that decade when the Mauraders joined the Order - so the relationship between Voldemort's supporters and more common criminals may change over that time too!