Most religious institutions were already established at the beginning of the Roman Kingdom and held an important role in Roman society. The concept of pax deorum ("peace of/with the gods") was a central part of Roman culture as it directly connected religious practices with the well-being of the state of Rome. The Romans adopted the myths of the Greek gods, renamed them (Zeus became Jupiter, Pallas Athena became Minerva, etc.) and connected these stories with Roman culture (the founding myth of Rome states for example that Romulus and Remus were descendants of the Trojan prince Aeneas).
This does indeed get me wondering how the Roman people could have accepted the Roman gods, as the Romans (at least a considerable portion of the population) also knew some of the stories of Greek mythology. In my opinion, they would have clearly spotted the huge similarities between the two religions and would have rejected the new religion as it looked like a poor imitation of the "more pure/ true religion", Greek mythology.
May someone explain?
Source: reddit post