I get the paradox of lack of evidence versus high probability but.....
Lack of evidence is based around what we currently assume and see as evidence and we've only been 'aware' of the possibility of life elsewhere in the universe for maybe 500 years tops, apart from a few, so they could have been coming and going for 13.8 billion years (less 500) and we wouldn't know.
We don't know enough about the universe yet to even get near this question so the paradox in relation to alien life is a non sequitur. The question posed comes from a source of assumed knowledge, this is flawed as the assumptions are just that.
I hope somebody finds life underground on Mars.
He is probably right about civilization destroying itself, or at least thinning itself out. I think if/when a nuclear bomb gets dropped, the devastation will be horrific, sufficient to brink all countries of the world into some sort of verifiable agreement.
I think he missed a possible cause of human extinction:
"Billionaire entrepreneur Elon Musk, physicist Stephen Hawking and other tech luminaries have signed an open letter warning against the dangers of starting a global arms race of artificial intelligence (AI) technology unless the United Nations supports a ban on weapons that humans "have no meaningful control over."
Killer robots are still my best guess.