He doesn't stumble.  He's steered every step of the way.  There are very few chapters in Changes where Harry is not being managed by some combination of a) the Merlin b) Eb c) Mab or Lea d) Uriel/the White God e) Odin.  It's not a complicated set of chances left to run, it's an operation micromanaged every step of the way.

Well nuerovore, while I agree we can't discount your theory of a group of Illuminati level conspirators controlling things from behind the scenes, neither is there much direct evidence to support it. Many events can be explained/justified if your theory is true, but by assuming the level of near omniscience and competence you give this proposed group you could easily link truly random and unrelated events (say me not having my morning tea causing a collapse of tea futures).  My main objection to this is largely personal in that such a conspiracy would be beyond complex with the potential for catastrophic failure if there is the equivalent of a rounding error in the plan. Depending upon the successful completion of, say, 200 events needing to happen in sequence just seems a needless complication. If such a conspiracy does exist in the Dresdenverse, I firmly expect Jim will show it toppling under its own weight simply because his universe seems to place a great store in free will and by its very nature such manipulation would be anti free will.