One of the most technically challenging things about reconnaissance satellites is dealing with the high speed at which the satellite moves over the target. A balloon flies much lower and vastly more slowly. It can loiter over an area, sucking in electronic signals and taking photographs with extremely high fidelity.

I don’t think the Chinese meant for this balloon to cross the United States. I believe they were testing it for use over other countries or perhaps for use during wartime. Their apology was way too quick for this to have been anything other than a genuine accident.