If you look more closely into this and many of the ebike battery fire stories they have a common element.
they were charging when they caught fire.
Cheap charger, cheap BMS, wrong type of charger, too strong of a charger, etc.
They never include enough details when it comes to the equipment in question to be able to make a determination, but given the fact that he was charging his bike in a public setting, I would almost hazard a guess that his bike was plugged into the wrong style of charger for the cell type in his battery. Charging a LiFePO4 cell like you would a LiON or vice versa will cause high stress and a ton of heat. Especially if it is a rapid charger.