Unless and until we either find life somewhere else or figure out how to make a living organism from scratch in a laboratory we have no idea how common or rare life (let alone intelligent life) is in the universe.
Making complex organic molecules is easy. Simply take hydrogen, oxygen, carbon, nitrogen, and a few other elements, put them in a compressed environment with an energy source, and stir them for a few million years. Gas giants are great for that.
How to make the jump from the most complex organic molecules to the simplest living organism is entirely unknown.
I’ll just say that astronomers estimate there are between 100 million to 400 million stars in our galaxy alone. The odds of us being alone in the galaxy are slim as far as I’m concerned.
I’ve always believed the universe is teeming with life, based on the fact that nothing in the observable universe happens just once.
From top to bottom, macro to micro, nothing in the universe happens once. There’s not just one galaxy, there are (minimum) hundreds of billions, if not trillions, of galaxies. And in those galaxies there’s not just one star, but hundreds of billions or trillions of stars, surrounded by literally innumerable planets. Irrefutable proof that nothing happens just once.
And on our planet life has taken many, many diverse forms, again from macro to micro, and multiple times. All spawned from the same universe that never creates anything just once. It’s impossible, in my mind, to believe the same pattern hasn’t happened countless times across the universe.