I'm all for taking precautions, but it seems a bit odd for them to conclude that the weather was "too dangerous" for performers, but not "too dangerous" for hundreds of fans to congregate to see the show. Seems like they would've cancelled the show entirely if the weather seemed hazardous enough. But I'm no expert. (I have no issues with lipsyncing or pre-recording vocals either; that's just showbiz)
I saw Weird Al live about 8 years ago and a huge storm rolled in about halfway through the show. They told everyone to head home and that the show was over, and they were right to do so; the drive back home was perilous with zero visibility for long stretches due to the heavy rain.