How did the commander Constantine come to power and become emperor?

Flavius ​​Valery Constantine (KONSTANTIN I) in his youth served in the army and participated in campaigns in Egypt and Persia.
In 305, Maximian and Diocletian resigned from themselves. Constantine’s father became emperor in the West.
Constantine moved to his father and took part in a campaign against the Picts in Britain.
After the death of his father in 306, he was proclaimed by the troops in August.
His authority was not recognized by everyone. Some considered him a Caesar.
It should be noted that at that time there were several August, which ruled over different lands and were not opposed to receiving land in control of another August.
In 307, Constantine married Maximian’s daughter, which forced him to be recognized as August.
But during the absence of Constantine, an attempt was made to seize power by Maximian. The latter was forced to commit suicide.
Further, Constantine gave his sister for August to Licinius.
Received him as an allies and began an aggressive campaign against Maxentius in Rome.
It should be noted that by that time Constantine already understood the meaning of Christianity and was baptized.
The campaign ended in success. Augustus Maxetius and his son were killed. On the way home from Rome, Licinius defeated Maximian Dazu.
For a long time, August 2 ruled in peace and harmony.
But the thirst for absolute power haunted. In 324, Licinius was defeated by Constantine.
Not disdaining marriages of convenience and the murder of a large number of people, Constantine receives full power.