I think one factor which is very important what nobody look at it, is that bitcoin was and will ever be independently. So thats why the most people also trust in the anonymoty of bitcoin. Of course there was a huge effect from the dark web. People start to buy like crazy drugs and other ilegal stuff and pay them with bitcoins. But if it was not like anonymous contos, it would not be so high. So there are many factors what caused the bitcoin boom.