Did you know that the Washington Arch in lower Manhattan was originally inscribed in Latin?
https://fineartamerica.com/featured/1-washington-square-arch-granger.html
CMOS sensors use a rolling shutter and when the lightning strikes it illuminates the entire frame spanning the shutter's traversing of the scene during the few milliseconds the rest of the frame on either side of the "beam" is before and after the lightning struck when the entire sky is not illuminated.