At a time when the Romans conquered other peoples of Italy, the custom was invented to take over the worship of at least some of his deities while destroying a hostile city.
The Romans did it for fear of the secret powers of powerful beings. They guessed that if the deity was taken away from the honor and sacrifices it was accustomed to, it could have revenge on the conquerors. However, if the god gets a new, sometimes better seat, he will show grace and friendship to a pious and hospitable city. Such ceremonial transfer of deities in Rome had its name: evocatio, or calling, from one place to another. In this way, the Romans took over the gods of the peoples that they conquered: Etruscan, Greek, Egyptian, etc.
