Here's one possibility: intelligent life is sufficiently rare yet the universe is sufficiently large that the universe contains a very large number (possibly even an infinite number) of intelligent civilisations, but they are all sufficiently distant from each other in space and/or time that the odds of any of them ever interacting with each other (or even knowing of each others' existence) is extremely low.
e.g. imagine a universe containing a million intelligent civilisations, but each of those intelligent civilisations is in a separate galaxy at least 100 million light years apart. If that is our universe, we might not encounter any of those other civilisations in the next million years. The odds of human extinction could easily be higher than the odds of having any contact with them.
e.g. imagine a universe containing a million intelligent civilisations, but each of those intelligent civilisations is in a separate galaxy at least 100 million light years apart. If that is our universe, we might not encounter any of those other civilisations in the next million years. The odds of human extinction could easily be higher than the odds of having any contact with them.