The ability to repeat disruptions targeted on specific groups generates changes in behavior (economic, social, and psychological) akin to an excessive tax. This is in contrast to large, one-off, attacks that cause massive disruption and then quickly dissipate as the targeted system returns to equilibrium. The standing order for this is:
...repetition is more important than scale....
Simple, low cost, easy, and repeatable (in that nobody is caught) attacks are both sustainable and generate the greatest potential returns. This doesn't mean that these attacks don't have a significant impact. Network effects from disruption almost always guarantee and outsized return -- the great is the enemy of the good enough.