Your reading it wrong.
Even AI says this,
“Sol Invictus, Latin for "Unconquered Sun," was a Roman religious title and concept that referred to the sun god. Sol Invictus was a relatively late addition to the Roman pantheon, and it gained significant prominence during the later Roman Empire, particularly in the 3rd century CE.
The worship of Sol Invictus was closely associated with the idea of an invincible and unconquerable sun, symbolizing strength, power, and endurance. It was also linked with the concept of the sun's rebirth and the lengthening of days after the winter solstice, which was a time of celebration in the Roman calendar.
The festival of Sol Invictus was established by the Roman Emperor Aurelian in the 3rd century CE, and it was celebrated on December 25th, coinciding with the winter solstice. This date was chosen because it marked the point in the year when the days start getting longer, signifying the "rebirth" of the sun. It's worth noting that the celebration of December 25th as the birthday of Jesus Christ in Christianity became prominent later, and some scholars believe that the choice of this date may have been influenced by the pre-existing celebration of Sol Invictus.
Sol Invictus was a syncretic deity, meaning that it absorbed elements from various other sun gods and deities, and its worship was part of a broader trend in the Roman Empire of combining and harmonizing different religious traditions.
The worship of Sol Invictus gradually declined with the rise of Christianity, which became the dominant religion in the Roman Empire. However, some aspects of the imagery and symbolism associated with Sol Invictus can be seen as influencing certain aspects of Christian iconography and the timing of the celebration of Christmas.”
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