I've been saying, only kind of jokingly, that a more likely outcome than arrest or Israel-directed assassination of Sinwar is Haniya (or his successor) taking him out to a field to talk about the alfalfa they're going to plant, and how Sinwar will get to feed the rabbits. Sinwar really fucked Hamas over here. Easy to lose sight of how good a thing they had going! It had tacit Israeli government support and was making a bunch of Hamas people fairly rich.
Anyways, from that point of view: yes, killing tens of thousands of civilians is certainly going to radicalize people and drive them into militant groups. But those groups might look more like the Al-Aqsa Martyrs Brigades than the Al-Qassam Brigades.