Ironically,some drug cartel do indeed gave candies to children in their area of power on some occasions.They use the carrot and stick method to maintain control, everybody knows that.Or do you mean how they pay for it?By any means available to them :money, goods, favours,coercion etc .They would readily use bitcoin like any other asset that they have access to .
This deserves its own reply. Some drug cartels employ people, build schools and road, etc. BECAUSE LAW ENFORCEMENT IS TOO AFRAID OR UNABLE TO STOP THEM!!! They are then able to win the peasants over through greed and the threat of violence.
If drug cartels were forced to use bitcoin, well first of all, they tend to be pretty stupid thugs. They would be easy pickings for cybercrime enforcement to lockdown in most cases. I can't even.