Not just soldering irons. Fans fail, sensors go bad, circuits short out and chips fail. Redundant safety devices are necessary!
I have seen fans fail to blow but still happily draw reasonable current. With a blocked inlet or stuck rotor, the fan will still draw power. Once found a cheap fan where the fan blades had become disconnected from the motor. A friction fit had failed.
The heater current drops during operation. Initial resistance of a cold heater will be highest, and the fuse will be sized accordingly to limit nuisance failures. The heater would not overload the fuse unless the ceramic support failed allowing the heater element to short.
To prevent a fire, a thermal fuse would be added in circuit with the heater. Best location would be in the power lead that goes through the center of the ceramic to the far end of the element. Value would be much higher than normal operating temperatures, but well below meltdown. Without this I doubt the device is actually CE rated.
Dave, please check: is there is a thermal fuse? It may have been ignored as it doesn't affect normal operation.