I don't think Silk Road etc constitute the actual majority of the black and grey markets enabled by cryptocurrency. It's just where most of the media attention is because of stuff like "assassination brokers" etc. Most of it is really mundane stuff, mostly drugs (of either kind). Which is also where long-term repeat customers are valuable, so sellers are hesitant to lose reputation through outright scams.
I don't think it's recovered from the silk road and alphabay era?