The universe is infinitely large and contains an almost infinite number of planets, so why shouldn't there also be infinite potential for other civilizations? Any civilization that travels in space, even at 0.1% the speed of light, could colonize large parts of the Milky Way in just a few million years, and that's not that much considering how long this galaxy has been around. But it seems infinitely empty like there's nobody out there but us, that's the Fermi paradox. This dictates that any civilization that finds it seeks to wipe out any other civilization it finds with immediate effect, and this paradox isn't all that stupid. This struggle between civilizations can also be observed on earth: a small animal is eaten by a larger one, but the larger one is helpless at the mercy of tan even larger one. A few years apart between civilizations can become a one-sided massacre. Imagine the legions of the romans fighting napoleon's army - they would perish meaningless. It's the same thing. Napoleon's army would have no chance against the weapons of the First World War, and these in turn would not stand a chance against modern fighter jets. So only a few years can be the downfall of entire civilizations. So the only way it seems to be here is to say nothing, be silent and hide because maybe there are only two kinds of civilizations in the universe: silent and dead. Every civilization could not only become dangerous for others, but the danger could come from oneself. So it would only be logical if extraterrestrial civilizations dominate the planet just like Earth.
Maybe both civilizations come with peaceful intentions but neither trusts the other and then it is only a matter of time - who will shoot first and wipe out the other civilization completely? Different civilizations could have very different levels of power. But maybe that is all a bit too pessimistic. Maybe there are extraterrestrial communities out there that live and trade peacefully with one another, because even humanity has slowly understood that progress is best achieved when we act peacefully and exchange ideas with one another. Maybe there are some other creatures out there just waiting for us to discover them and join them.