So what can France and other countries do to stem the tide of such attacks?
Enforce laws on the books and if the penalties are not harsh enough, increase them. It isn't just for crypto crimes, but for any: if you are violent or rob someone, you need to be out of the general population for a long time and learn to control yourself.
That's the sad reality in this life. We are vulnerable from these bad actors in the society even if we are not doing anything. We can't deny the fact that even if we are very cautious, still, there are people who will do such bad act to other people. They have their own reasons and we can't deny the fact that some of them are in desperate position.