Not sure what happened, but the protective lens on my GoPro Hero 7 got a nasty crack while we were riding in Colorado. GoPro had a good guide on replacing the protective lens and it’s fairly easy to do.

GoPro Guide: https://gopro.com/help/articles/how_to/How-Do-You-Replace-a-Broken-Lens
Replacement Protective Lens on Amazon: https://amzn.to/2KGAfU5