The human race is incredibly stupid. The fact that we exist is proof life in the universe is possible. Infinite opportunities for life to exist makes it not only possible but extremely plausible. The infinite opportunities of species to evolve through the generations some leave their home planet. The unidentified objects seen in Earth's atmosphere over countless generations proves not only are we not alone but they are intentionally leaving us alone. An ant it's not a threat. But when an ant starts building and detonating larger-scale weapons  concerned attention may be drawn. For all we know there's an outpost on the moon and the planet is being safeguarded for the species that will truly inhabit this planet when the time is right.