i don’t know if this needs to be said but people often overlook the second part of his, “why does a man seek to destroy the world?"—"for immortality and power” when talking about jonah’s motivations. sure, he calls death ‘the last and greatest terror’ but everything else we hear from him points towards a lifelong desire of wanting to be in control, which is why in 92 he unnecessarily begins his confession with “i have done everything because i wished to”. and i think that distinction between the fear of death and the need for control is important because people bring up his reasoning of 'what i considered an inevitable transformation’ when talking about why he did all that. and it may have begun as such, but he and gertrude also figured out that the rituals were too flawed to work anyway. when he hires jon as head archivist that sense of urgency is just not there, it was no longer a proper 'race’ to conduct your own ritual, he did not have to immediately end the world.
what i’m saying is that he caused the apocalypse because he was never going to be happy with the world as it was. because the horror in the magnus archives universe operates on one basic tenet - that your life can be destroyed at any time, through absolutely no fault of your own.
MAG 106 - “A Matter of Perspective” // MAG 118 - “Stranger and Stranger” // MAG 160 - “The Eye Opens” // MAG 117 - “Testament”
the “dark and horrible reality” of the world, and in turn the specific existential dread that grips him is that of chance. to be told that you did nothing blameworthy inspires a specific feeling of powerlessness—that if you didn’t do anything wrong, there is nothing you can do, no personal behaviour you can correct to stop it from happening again. and he understands this quite well, it’s in the way whenever he really wants to twist the knife he tells them it was luck, but that doesn’t comfort you does it!
which is why the use of “freedom” here is very telling. in their universe you are always going to be a victim of the cruel caprice of gods, that in itself is a blow against all notions of personal agency and control. how can you be truly free when malevolent cosmic forces govern the world and can ruin your life without warning at any time? and 160 is above all, an attempt at escaping the grasp of the fears entirely. it’s not just about death, it’s about wanting to be in charge so no threat can touch him again and in their world you can only achieve that by causing the apocalypse. he will be free (or, at least the closest thing to being free in their world) and it will be at the expense of the entire world.