פירוש על עבודה זרה 86:13

The Talmud here cites the fascinating case of a synagogue in Nehardea. The synagogue is called “Shaf Veyativ” which means “destroyed and rebuilt,” and indeed, there does seem to have been a famous destruction of the Jewish community in Nehardea in 247 and then the community was rebuilt. Fascinatingly, there was a statue in this synagogue, certainly something that the rabbis would not have been comfortable with. Rabbis attended this synagogue, but it does not seem that they were leaders of it, nor were they consulted on questions of behavior there. So if Shmuel’s father and Levi attended this synagogue, they must not have been too worried that someone would think they’re worshipping idols.
The Talmud resolves the issue by saying that if many people are around, then we’re not concerned that someone will worship the statue. It seems that the presence of others will act as a deterrent (there are things one might do in private that one will not do in public).