It tends to happen when:

1) You must have a crowded optical disc as a precursor (low cup to disc ratio). Genetic and can be tested

2) You have stiff veins/arteries due to poor metabolic/cardio health

3) when blood pressure drops too much, blood flow can get cut off to the optical nerve temporarily due to reliance on high blood pressure due to 2

4) Due to loss of blood flow, optic nerve swells and closes blood flow into the eye due to 1