i think that they create these websites same as normal ones, just main difference is that they sell illegal stuff there, but i am sure that there is tutorial for that
Dark marketplaces are very bad. There are indeed a lot of scammers and you can buy some illegal stuff and that is not good. But you cant stop people to not using that and that is the problem but try as much you can. you do that.
DArk places is the place all you can see are illegal thats why its dark places.. unlike deep web.
Thats why bitcoin has a very bad name in some countries because of this they can transfer money without know owners,.