Why is Julius Caesar called Divine?

In Roman history, Romulus, the founder of Rome, was accepted as Quirinus. Quirinius was the early god of war, identified with Mars. In later times, he was known as Janus Quirinius. The Sabines, ancient Italian people who lived in the Appenine mountains, erected an altar for Quirinius at the Quirinius hill, one of the seven hills of Rome. Romulus was the first to be raised from human to divine.
The Roman Republic did not make any man divine. This all changed with Julius Caesar. After he was assassinated ("Et tu, Brute"), he was raised to the divine status, and hence he was Julius Caesar the Divine.
In his book on the life of the twelve Caesars, Suetonius expresses his thoughts on the apotheosis of Romulus as a cover story to hide his suspicious disappearance, which could be associated with the Patricians conspiracy. The divine status of Caesar was probably also related to the conspiracy, although Caesar being referred as a living divine started even before his death. It was made official by Augustus in 42 B.C.E.


References

Imperial Cult of Ancient Rome  https://en.wikipedia.org/wiki/Imperial_cult_of_ancient_Rome#cite_note-38

Temple of Caesar

https://en.wikipedia.org/wiki/Temple_of_Caesar

Julius Caesar

https://en.wikipedia.org/wiki/Julius_Caesar