Some many chances for early life to have hung on, delayed change, stalled evolution. These early organisms hung on for 100's of millions of years, dominating and out-competing later forms until gradually they were in turn out-competed.

Same with Dinosaurs! They dominated for 200M years. But for a chance asteroid we could still be a planet of dinosaurs. No sign of them giving up in the fossil record.

We find other planets with life, likely will be stalled in one of these cul-de-sacs. Our own existance can be explained by observer's paradox - we didn't get stalled which is why we're here which is why we can wonder about these things!