The culture and self-conception of classical Rome (like all pre-modern cultures) was that of a complete or totalizing culture — in the sense that civic or political life and religious life were not separated and compartmentalized; the modern notion of the former being public and the latter being private were not then present. The polis and the economy spanned the whole of material phenomenon as well as spiritual or metaphysical phenomenon. This is not to say that there was homogeneity and imposition of one worldview — within the broader cultural substrate, there was a lot of diversity of specific beliefs about deities, morality, the relationship of power and authority, etc.
In this milieu, marriage itself was thought to be have an ontological, objective significance as a phenomenon in reality (as is still the case today among most religious people), and was thought of as not being merely a personal subjective construct.
Given this, we can begin to understand that when Emperor Claudius Gothicus “banned marriage” for the purpose of recruiting young men for his wars, it would be effective because the Emperor spoke as a type of vicar of the pantheon of the deities, i.e. the ultimate being(s) behind all reality, and his laws were held to actually sanction metaphysical reality. A young man could not simply state that the person he lived with was his wife, if such a thing was not allowed. In his own mind, he could barely even conceive of what we would call an anarchistic stance against the Emperor and the Roman law.
It is into this scene that St. Valentine burst in with his counter-polis and counter-economy of blessing and celebrating Christian marriage. In microcosm, this is what the Gospel did and does — it is an anarchistic subversive proclamation of an entire complete culture, a Kingdom, a polis, an economy that is whole, i.e. spanning all of material and metaphysical reality, and is in conflict, or opposition, or war (albeit, rejecting violence) against the then current Roman politico-spiritual reality, in every sense.
Therefore, St. Valentine in a true sense opposed the Roman Empire and was effectively handicapping its power and evil. For this, he was martyred according to some traditional hagiographies.
“In the 268 AD the Roman Empire was ruled by Emperor Claudius II, or Claudius Gothicus. Claudius was generally tolerant of most religious policies, but persecuted the Church. He passed an edict forbidding the young to marry, based off of the belief that unmarried soldiers fought better than married soldiers, who were constantly worried for the health and well-being of their family in the soldier’s absence, or what would happen to the family in the event of the soldier’s death. Polygamy was also more popular during this time, though much against the Christian teachings of the sanctity of marriage between one man and one woman. Despite the restricting edict, marriage was the special mission of St. Valentine. He secretly married young lovers in the Church, going against Roman law to secure the bonds of love between young couples. However, the Roman authorities eventually captured and imprisoned him. After imprisonment and grueling torture, St. Valentine was put before the Roman law for his acts of sealing love in the Church against the laws of the Emperor.”
[https://catholicsaintmedals.com/saints/st-valentine/]
It is entirely fitting that the above hagiography that focusses on romantic love and marriage fits nicely in the overall context of St. Valentine’s broader mission of building and extending the Kingdom of his Lord and God, Jesus Christ.
“A common hagiography describes Saint Valentine as a priest of Rome or as the former Bishop of Terni, an important town of Umbria, in central Italy. While under house arrest of Judge Asterius, and discussing his faith with him, he was discussing the validity of Jesus. The judge put him to the test and brought to him the judge's adopted blind daughter. If he succeeded in restoring the girl's sight, Asterius would do whatever he asked. St. Valentine, praying to God, laid his hands on her eyes and the child's vision was restored. Immediately humbled, the judge asked him what he should do. He replied that all of the idols around the judge's house should be broken, and that the judge should fast for three days and then undergo the Christian sacrament of baptism. The judge obeyed and, as a result of his fasting and prayer, freed all the Christian inmates under his authority. The judge, his family, and his forty-four member household of adult family members and servants were baptized. St. Valentine was later arrested again for continuing to evangelize and was sent to the prefect of Rome, to the emperor Claudius Gothicus (Claudius II) himself. Claudius took a liking to him until he tried to convince Claudius to embrace Christianity, whereupon Claudius refused and condemned St. Valentine to death, commanding that he either renounce his faith or he would be beaten with clubs and beheaded. He refused and Claudius' command was executed outside the Flaminian Gate February 14, 269.”
[sourced from multiple; collected at https://en.wikipedia.org/wiki/Saint_Valentine#Hagiography_and_testimony]