The Temple of Jupiter was severely damaged during the earthquake of 62 A.D. It had not been fully rebuilt when the city was buried by the volcano in 79 A.D.
It's unlikely that public taxes were used to support the sites of worship. Therefore, the priests and priestesses of the various temples in Pompeii must have engaged in some competitive practices to attract sufficient clients to support their activities. It reminds me of the various churches scattered throughout every American town, all of them in competition with each other, but tolerant and superficially supportive of each other. Different citizens of Pompeii no doubt had their favorite gods or goddesses, but many merely enjoyed the various religious holidays without much true devotion to the religion. By the first century, many Romans had abandoned any real faith in the pagan deities. Ancestor worship and veneration of dead relatives was common, however, and shrines to them were found in every house in Pompeii.
Interestingly, the only temple in town that had been completely rebuilt following the earthquake of 62 A.D. was that of the Egyptian deity Isis. She apparently had a large number of devoted followers who provided sufficient funding to rebuild the Temple of Isis completely after the earthquake. There was a "fashionable" interest in Egyptian culture and religion in the Roman Empire in those days. A massive quantity of gems and coins were discovered at the temple of Isis during excavations. (This Web site has no photos of the Temple of Isis because it was always closed in the mid-1980's. It was open to tourists when we visited in 1999.)