ya right... any idiot knows the path of the jet stream so htf is a balloon going to be blown off course!??
The jet stream is NOT the simplistic path you see drawn on your local TV’s weathercast for the average Bub or Bubbette. Nor does it stay in the same place for long. Wind velocity (that’s a vector, not just magnitude) changes with altitude and doesn’t always match a prediction anyway. How often do passenger airliners have to make an unexpected adjustment? All the time, but they have far more capacity to maneuver, thank heavens. (Yeah, bad pun.)
Balloons can’t make quick adjustments — guess wrong, and your balloon can be 500 miles off course, getting worse, and no way to recover. I imagine the Chinese just figured “Well, if it’s going that way, maybe we can adjust and float over something else...”
Did your weather forecast “fail to verify” in substantial fashion? Good chance the jet stream did something not forecast.