Before bony fish ascended to their current dominance, there were plenty of other fast predators in the sea. If lack of predators is a requirement for cephalopod civilization, the window probably closes much earlier than the Cretaceous.
An alternative, possibly more optimistic (?) hypothesis: the first step of their civilization would be collective defense from large predators. Population concentrations would then make farming very advantageous. Yes, I'm more a scifi writer than biologist.
It could be as simple as the evolution of fish jaws making the mollusc shell insufficient defense. Or fish eyes/pressure sense/etc developing enough to notice hiding molluscs better. It's plausible that earlier predators were below the threshold of extinction-level risk. Flipping the perspective, humans were below an extinction-level risk for most large land animals for a long time.
An alternative, possibly more optimistic (?) hypothesis: the first step of their civilization would be collective defense from large predators. Population concentrations would then make farming very advantageous. Yes, I'm more a scifi writer than biologist.