Indeed, one of the most head-scratching solutions to the Fermi Paradox might be our underestimate of ice moons as cradles of life. Inhabitants of worlds such as Europa or Enceladus could happen to become prevalent in the Universe, numerically, over species that dwell on the terrestrial-styled surface, like humans; they, however, may have little if any need to develop space travel, even less galactic kingdoms or empires, because of lack of proper resources or even stimuli to break beyond the walls of ice. After all, by breaking the ice shell in sufficient number of places they'd eventually force the very ocean where they evolved to siphon into outer space. Hence they’re destined to remain in what would look like darkest solitary confinement cell in human eyes, mostly unknown or totally unaccessible to us.