There are many external reasons, the current is too large, causing burnout or resistance changes. The soldered circuit board is deformed due to external force, which causes the resistor to break (especially the most common in surface-mount resistors). The heat generated cannot be discharged even if the resistor is operated in an overheated environment and is easily damaged...
There are several common internal reasons: the roughness of the resistance and the uneven material lead to changes in the local resistance. The power selection is very close to the maximum power point. When the interference is instantaneous, the resistance is damaged...
