No serious astrophysicist is claiming there is no extraterrestrial life. We haven't found any definitive evidence yet, but that's just because our sample so far has been tiny.
Nobody claimed there was no extraterrestrial life. Most expect some life with at least some algae. Just chances for intelligent life, as more data comes in, turns out to be rather small and with a reasonable chance we're the only one in this galaxy. The values originally used in the Drake equation were very optimistic.
That would be very surprising if it were true, considering the incomprehensively vast numbers of stars and planets out there. I wonder what the equivalent of crying in the shower would be for some alien though? Maybe that is our unique trait.
If it were not true then that would be the actual surprise. The probability for life to form has been computed over and over during the past century, incorporating ever more gains in scientific knowledge, and it is on the order of 10-100, meaning that there likely is no other life in at least our galaxy.
There's no one that can make the estimate accurately right now. Any calculation like that is going to rest on lots on many wild estimates and unknowns. Happy to look at it if you have a source though.
We're working with an n of 1 basically. If you're talking about the drake equation, many of those terms are wild estimates that we simply don't know the answer to, it's more of a thought experiment. In the course of astronomy history when we've assumed uniqueness about earth or our cosmic situation we've generally been wrong. Unfortunately the vast distances between stars make an estimation of life in the universe difficult with current technology, as there is so much we can't observe.
But there's billions of stars in the galaxy, billions more planets, and septillions of star systems in the universe with billions of years for life to happen. Intelligent life has happened at least once because we're here. Even in the tiny slice of planets we've been able to observe in some way in our narrow little corner of the galaxy we've found numerous ones in the "goldilocks" zone. It would be utterly shocking if we were the only intelligent life out there, even more shocking if our planet had the only life. And all of this assumes we know what kinds of life are possible! We've only ever seen our own type of chemistry.
Don't mistake this for me saying we've been visited by aliens in UFOs or something though, not saying that at all.