"Criminals need the internet to make money. They do not want to kill the net and they do not want to make it unusable for their victims."
But the tragedy of the commons shows how a group of criminals, none of whom want to kill off the net may end up doing so anyway because they are (a) greedy and (b) unable to coordinate their actions to keep their greed in check.
The net is a classic common pool resource, which means that Tragedy of the Commons is a real threat when each additional attack increases the profit to an individual black hat while reducing the collective profits taken by all of the black hats (the marginal utility to the individual is positive, but the marginal utility to the whole dark economy is negative). Over-fishing is a classic example.
Elinor Ostrom showed that in real life, common pool resources can be successfully managed against this threat, but only when there is a mechanism to set and enforce rules (either through formal governance or through informal norms and sanctions). Essentially, unless black hats develop their own dark government to effectively control and limit attacks, there is a real possibility, in principle at least, of tragedy of the commons bringing down the net.
However, just because it is possible does not make it likely. I am not qualified to assess the probability of this kind of collapse.