There are many things to understand before we start looking into possible explanations given by historians, but before that let us know one thing: The love between Radha and Krishna was not one like some mundane relationship now a days between young girls and young boys.
The Love between Radha and Krishna is called Parakiya. They never got to marry each other and hence Radha was married to someone else, but she and Krishna were friends from childhood. Krishna used to play his flute and Radharani used to hear the mesmerizing song played by him. They were like Kishora-Kishori but without inebriety.
Parakiya – meaning love ,not by marriage ,but by friendship. In the spiritual world it is considered pure but in the modern world it is considered adultery to fall in love with someone else’s wife or husband. It does not means that Radha and Krishna were commiting any kind of sin, the history reveals the story further.
When Krishna was a child then Radha was asked to accompany him back home. And so during the journey in their childhood forms, they were walking down in Bandiravan( a beautiful sacred garden). They stood beneath the Banyan tree and by their mystical ways attained their youthful form. Lord Brahma became the priest for the wedding and devi – devtas were saakshi of the wedding. Lord Brahma performed the rites of the wedding as mentioned in the Vedic Culture. During the wedding Radha’s sari was tied to Krishna’s Dhoti. When the ceremony was over and the guest had left, they assumed their childhood forms back. Radha left Krishna at his mother’s(Yasodha) house and walked back home.
In this way, it is actually believed that even though Radha and Krishna in Human self never married to each other but they were married in their Higher Power Self. Radha is said to have married to Abhimanyu.
According to Vedas, Krishna is said to be the only male(Purusha), and everyone else is prakriti or female. So , as understood Krishna was everyone’s Pati, or every woman’s husband.