[Filligree]

> Honestly as the other response says, indeed there is a parallel universe part to it.. For which I didn't really understand it relation to "dust".

The other universes count as part of the "dust".

The characters in the book thought it would be only random 'simulations' that accidentally happen sometime in the universe's infinite future that kept running them -- that is, literal dust.

They were wrong. Simulations in entirely disjoint universes also count, and aren't nearly as predictable.