This video, the map elsewhere in this subthread, and the stream recording give a nicely detailed view into what went down. It seems like everything went like it was supposed to in terms of pre-warning, but based on the video the information didn't make it to pilots with coinciding flight plans until after the fact.

As far as I understand airline pilots have a high level of authority and diverting probably was the right call depending on the lag between seeing it and knowing what it was or if there was a risk of debris reaching them. They wouldn't necessarily know how high it got or what that means for debris.