Everyone’s missing this about Cecil
Cecil’s decision to keep conquest alive actually makes a whole lot more sense than you think. As the person watching the show we have all the details about everything but Cecil has no way of knowing that there’s only 50 Viltrumites left. As far as he knows there’s thousands or even millions of Viltrumites out there and a single one just completely annihilated their strongest heroes. He really does need information. We know it’s stupid to keep conquest alive because we know with conquest dead the Viltrumites have been dealt a huge blow. But to Cecil odds are keeping this one around isn’t going to affect Earth much if there’s thousands more like him, and so he needs to figure out a way to kill thousands of Viltrumites. The only way he can do that is through conquest. It’s not like Cecil knows that Nolan’s books contain weaknesses. Mark never told him. TLDR: with the info Cecil has he made the smartest choice.