Technology development and having pleasure. Hedonist cultures or civilizations on the way...
Diversification - civilizations that privilege: understanding, war, pleasure, obedience, richness, longevity, power, beauty, love and companionship, stillness, openness and diversification, homogeneity, respect, etc...
Engineered planets to serve the civilization's needs. Genetically modified animals, trees, engineered surroundings, weather, even continents, etc. A cozy house-planet. disadvantages: everything they would see would be a mirror of themselves, no novelty, no past, no different histories, a less diverse world?
Effects of war
nuclear war, in principle would let some humans alive, if technological infrastructures survives society as we know it would only need a few centuries to reemerge. If all the major technologies were destroyed, including books etc, then we are looking at millennia for for societies to recover to their present level.
Biological weapons and other doomsday devices: if all humans are destroyed or unable to reproduce, then we are looking at a time scale of hundreds of thousands of years for a civilizational animal to reemerge. If all primates were destroyed we would obviously be looking at a timescale of millions of years! So, a surviving couple may not seem much in the aftermath of a global war, but it would make a difference of millions of years