This exercise was not intended to blow a cargo airliner out of the sky. Nor was it intended to blow up a synagogue, for what should be obvious reasons.
This was an exercise. A well published exercise at that. It's intent was met.
The senders of the "package" had no idea on how it would be routed with the ultimate destination being the U.S.
They know now. Exactly.
And will probably plan their next action based on what they've learned. Using different routings.
No conspiracy involved. No tin-foil hats need be donned. It's tradecraft, pure and simple.