The answer to 'why is my switch tripping breaker' is that the switch is likely overloading the circuit. This can happen if the switch is controlling too many electrical devices, if there is a short circuit in the wiring, or if the switch itself is faulty. Symptoms may include the breaker tripping repeatedly when the switch is turned on.
To troubleshoot, first unplug any devices connected to the switch and turn it on. If the breaker still trips, there may be an issue with the wiring or the switch itself. You can try replacing the switch, but if the problem persists, it's best to call a licensed electrician to inspect the circuit and make any necessary repairs.