The wattage refers only to the power consumption of the machine but tells you nothing of the power efficiency or the amount of force the mechanical parts are built to handle. The problem with this value is that it is seen as a selling point in the consumer market and building a machine with a high power consumption is a trivial task from an engineers ...
Simple, the motor of this mixer, when using the dough hook, will be overloaded at any other setting but 2. (They are not concerned about the temperature of your dough)
Bottom line, this machine is underpowered for this job.
A KitchenAid mixer does not have adjustable gearing; at low speeds it’s being run at low power. If run at low power with a viscous, resistant load like bread dough it can end up stalling, either continuously or repeatedly during the knead. This can overheat the motor and reduce its lifetime.