Dropped my iPhone X. No cracks but display gone black.

There could be a few causes, the most obvious being the OLED screen could have damage underneath the glass that is keeping the screen from powering on and in this case you would need a display replacement.

Another possibility is it could be software related have you tried to do the soft reset of the phone by tapping volume up then volume down and holding the power button until the phone power cycles? I have seen a few instances where this happens and does fix the problem.

The only next step that you could take would be opening up the phone and reconnecting the display connections to make sure nothing came loose if that doesn’t work then you definitely need a display replacement.