Yes, the idea that the stars were distant suns has been around for thousands of years, so we can say that the real question here is, why was it so widely rejected by almost all astronomers who were introduced to the idea? One can try to look at the reasons that Aristarchus' heliocentric model was rejected by his peers, but unfortunately, no debate on those reasons has survived. An incorrect answer we often see is the absence of observable stellar parallax, but Aristarchus' model already accounted for that by making the stars so far away-- they certainly can't be suns unless they are so far that no parallax would be seen anyway. So what was the real reason that this idea was so slow to take hold, even after Galileo showed that the white swath of the Milky Way resolves into individual stars in a telescope?
I suspect we will never know, because very little of that ancient debate actually survives. Certainly the ancient Greeks did not have access to any data that could resolve the issue, it would always have to come down to one's world view, just as heliocentrism vs. geocentrism did. Ironically, general relativity tells us that latter distinction is purely one of the chosen coordinates, whereas the fact that stars are distant suns is an actually testable issue, and is demonstrable from their spectra and their parallax, neither of which were accessible to the ancients. Maybe we should start in good old England, and try to understand why even in the time of Herschel, the idea had still not caught on! No doubt it required better spectrographs to prove, but why was it always so philosophically objectionable that it was not immediately expected to be true? We generally favor unification, so why not for stars and the Sun?
