Web’s back-up plan is basically self-fulfilling prophecy
Let me explain!
First the back up plan of the Mother of puppet’s if any ritual ever succeeded is The Hilltop Road - the somewhere marked by all fears. All the fears are also captured into tapes which could pull all the them into another dimension with right cataclysmic event, right? (Okay, I might simplify it or straight out mess up some detail but not the point now)
Annabelle said that no one knows how it’ll go in the new reality and someone performs successful ritual again. So it’s really just a way how to escape from the End and get a new victims to feed on.
But for such a back up plan the Web needed to find the best person to record the tapes - Jon. And so the Web started coercing Jon, giving him the right pushes, leading him and also giving him on silver plate to Jonah Magnus.
I mean… Wouldn’t it be much easier just keep preventing rituals from happening? Only one who actually managed to figure out way for ritual to works was Jonah. Wouldn’t it be easier to kill him? Or if it’s not subtle enough then just keep sending useless Archivists his way?
Or maybe at least literally not give him the one perfect person which Web picked? (even if the Web needed Jon to work for the Eye and also be marked by all entities how hard would it be to let Jonah’s fucking “Apologies for the deception…” to get lost in mail?)
So my conclusion is that if the Web never started creating a back up plan they might as well not need any back up plan.
I’m not saying that the Web basically played itself but it did.