i do believe that one of the very reason why bitcoin become popular during its early stages was due to the support or usage obtained from criminal activitues.
We cant deny the fact that bitcoin has been by criminal since they have also seen the advantage of using it to conceal their transactions.
It would be naive to think criminal activity wasn't a major factor back in the day, but now most of the users of bitcoin are traders and users which want to earn money in a legal way, this is nothing new, a significant number of new technologies are adopted first by the military or by criminals so I don't think bitcoin is unique in that aspect but thank god we've left those years behind us.
Everything starts at the bottom I guess since there where less people using bitcoin back then they saw it as an opportunity to use it as a medium on making their illegal transactions but still there are people using it for themselves. Especially now a days that earning bitcoin is a great source of income a lot of people are engaging to use this and they cannot really identify who is using it for illegal transactions because you reamain anonymous through out the process.