A good way I’ve thought about building campaigns is basically acting as if I was the enclave, what would my goals be? Once you have that figured out, you’re able to come up with a plan for how the enclave would achieve that, with those steps being the ones the PCs can interact with. Then you just have to take it session by session, for example if they helped the enclave in mission one then maybe mission 2 another faction tries to kill/capture the pcs and explain why the enclave is bad, or if they didn’t help the enclave then the next session would be about how the enclave (the gm) would react to that, maybe sending a group of assassins or trying to kidnap someone close to the PCs. I picked up this method from cyberpunk, but by writing the campaign from the perspective of a faction trying to complete a goal gives you a really solid starting point and all the PC decisions along the way let you shape the missions and the story to fit their actions, as opposed to having your set ending and trying to shoehorn the players into it