I’m still trying to figure out why someone would be “speeding” on a charity ride. Anyway, I’m sorry for her loss and for the child who will not know/grow up withou his father.
Fit bikers who go on long distance rides usually compete with themselves, if not other riders. If he went into a curve at a high speed and his rear wheel hit a stone (happened to me once, I know) the bike could have shot out from under him, sending him into the car’s path.