Why is the led lamp burned out?

If it is connected directly, there is no current limiting resistor. Almost all battery voltage drops fall on the LED lights. The actual voltage and current exceed the rated voltage and rated current. The LED lights have been in overload work, accelerating the aging process, and the life of the LED lights is quickly abused by the button battery to so much a little bit.
And then connect other resistors, at the moment of power-on, because the equivalent circuit of the LED lamp is a junction capacitor circuit. According to the principle of switching, the capacitive current is abrupt at the moment of power-on. At the moment of power-on, the inside of the LED is equivalent to a short circuit. The instantaneous current is greater than the rated current and directly kills the LED lamp in the critical late stage. LED breakdown and short circuit, causing burnout.