I wonder if there's a form of cognitive bias where an unknown is treated as an absence rather than unknown, or rather a local known is extrapolated into a global one. We have fairly high confidence that there's not other intelligent life in our solar system. Not much is known beyond that. One extrapolation is that the universe is more of that. The other is that we exist as evidence and that pattern repeats elsewhere.
A multiverse I can equally accept as not. What I would find far more incomprehensible is if we were to discover with certainty that we were the only intelligent life in the universe.