We have no evidence to explain the what led to the formation biological life. However, given what we know about how evolution works, it is at least plausible (and likely) that some chemical process became repeatable and eventually led to biology. How is speculation because those earliest life forms weren’t complex enough to leave traces that would survive the test of time.
Do you have another explanation that’s based on evidence, or are you gonna make something up? I’m sure you will, so I’m going to beat you to it and say THE FLYING SPAGHETTI MONSTER DID IT! :)