What about the fuse? It should have prevented this. Was it removed?

IMO if you didn’t tamper with the space cell at all it’s enertions fault. The battery is supposed to have a BMS and fuse in place to prevent this sort of thing. If your battery caught fire then the short must have been internal since the BMS and fuse did nothing.

Was your battery damaged beforehand? What was your enclosure like? Did you run over anything that could have pierced it?