Why is calcium oxide CaO, and not CaO2?

Ca’s charge is 2 + and O’s charge is 2-. When you cross the charges it would be Ca2O2 and you would simplify to Ca1O1 and the ones are implied so just CaO

The Calcium ion is an Alkaline earth metal and wants to give up the 2 s orbital elections and become a + 2 cation.

Oxygen has six valence electrons and is looking to gain two electrons to complete the octet (8) electron count in the valence shell making it a - 2 anion.

When the charges of the Calcium + 2 and the Oxygen - 2 are equal and opposite, the ions for an electrical attraction. (Remember Paula Abdul told us "Opposites Attract")

This one to one ratio of charges makes the formula CaO