looks more like the explosion happened underneath and then went upwards through the rear of the truck, the first frame of it shows that the underside is engulfed before any of the windows even have a hint of a flame showing through them. Seems more like a dodgy battery blew up.
One of the videos has firework noises on it, and another one has little things visibly shooting around like fireworks after the explosion. Maybe for a change the Tesla wasn't the cause of this fire.
Or the truck bed. Definitely doesn't look like a standard battery fire. Either it was a really bad fireworks accident, or the driver just filled the bed with explosives and rigged it to blow. I guess we'll know soon enough.
Cybertrucks have a window between the cabin and the cargo area. It looks like the window (all the vehicle's windows) failed during the explosion and the fire in the cargo area exited through the cabin