Glad they mentioned Hickman's FF run. Everything after the "Forever" arc was set up for his Avengers run and there are enough clues prior to "Forever" to make you wonder if this started as a Fantastic Four arc that just grew into an Avengers event.

Funny aside: I was actually rereading Age of Apocalypse and 1602 and realized that while they probably aren't seeds for Secret Wars, they do both have a theme that leads into Secret Wars. Namely the Marvel Multiverse has a long history of being very fragile. They almost lost the whole Multiverse in AoA and in 1602 because of actions taken by time travelers originating from Earth itself. There's even a diagram in the M'Kraan Crystal that looks like it's the beta version of an Incursion showing how the destruction of one universe imperils those around it and eventually the whole of the multiverse.

Once you go back and read that stuff, it becomes a lot easier to understand that someone could possibly start the Incursions in Hickman's run. It doesn't seem that hard to really put the multiverse in danger.