Two incompatible hypotheses reinforce a logical conclusion.
Hypothesis number one. For life to spring up by accident is about as likely a a wind blowing across a junkyard assembling the junk into a jetliner. Therefore corollary one there must be an intelligent plan; or corollary two, life was transported here from somewhere else (but then where did it start).
Hypothesis number two there are so many planets, there must be life as we know it on x percent of the planets.
Well if the odds of life are basically one chance in infinity and there are an infinite number of planets, then logically the odds of life on just one of those planets is one. Here we are. I know that the mathematicians are about to pounce but we are dealing in an area where Newtonian or even Einsteinian logic won't help.
So far no person using scientific methodology can explain why there is life here or anywhere in the universe. It is the only true miracle perhaps an incredibly unlikely event happened just once on one minor planet circling a minor star in an unremarkable galaxy. The right combination of carbon based compounds at the right temperature and pressure and entropy and enthalpy and charge came together in just the right way to create something that never existed before: a simple life form, perhaps a virus, or prion, or something long extinct that had the ability to reproduce and to mutate into something more complex. It only had to happen once.