It would be comforting if they were stupid. In reality they are succeeding in forming their caliphate. They do know how to use BTC and do use it. This should come as no surprise to anyone. DAESH has shown an ability to use technology in furtherance of their media, communication, and surveillance capabilities. They are not anti-technology.
This is also not a reason to disparage bitcoin. It's just money and all sorts of people are attracted to that. Just as DAESH striking gold coins is no reason to avoid gold.