1. Early earth had no ozone layer, which means it was most likely extremely hot.
2. Young earth had no oxygen and life needs oxygen in order to survive.
3. There where so many natural disasters happening all the time, like volcanic eruptions and constant impact with meteorites and asteroids.
-Extra one (4. Earth originally had no ocean and water. Oceans eventually formed from the water vapor released from the volcanic eruptions, but before that there was nothing.)