My node mcu isnt turning on when connecting 3.3V to VIN
As it turns on when powered through USB, so, it seems that the chip isnt't dead.
How did you wired it? Are you connecting 3.3V to 3.3V NodeMCU's pins?
The correct way of powering a NodeMCU is with +5V in Vin; it has a onboard voltage regulator, the same one that converts USB's 5V.
If the board is powered with 5V, 3.3v pins are outputs of the onboard voltage regulator, that could be used for powering 3.3V sensors.