For example a 960 watt fan - fairly typical of the cabin air fan, at 12 volts would need 80 amps, whereas at 48 volts would need only 20 amps. (Power in watts = Current in Amps * Voltage)

If you have a bad connection in that cable of 0.01 ohms, then that bad connection would generate 64 watts of heat on the 12v/80a system (enough to melt the plastic on the cable and start a fire), whereas on the 48v/20a system it would only make 4 watts of heat (probably safe). (Power in Watts = Current in Amps Squared * Resistance in Ohms).