It's been a long time since I read Asimov's galactic-scale SF novels, but it postulated a universe where only humans had intelligence.

I dimly remember one of his series that involved time travel where it was explained that time travelers had gone to a great deal of trouble in the distant past to set this unique situation up...

Who knows how many coincidences were involved in evolving intelligence? Or even multi-cellular life? We only have one real data point.

Even if we detect a planet around another star that seems to have life (free oxygen in the atmosphere or something), it could still just be one-celled stuff. That's how most of our own history went. Initial evolution to complex life forms takes a LOT of time. Fortunately, once you've packed the DNA with a hundred million years of useful templates, things can go a lot faster.