it just kinda happened. Complexity of the inorganic kept on increasing till it discovered the trick of self replication with errors then BOOM, life.
Where exactly you wish the line that says life started here... is a subject for debate but fairly arbatary in the gradual change from in-organnic to organic...
sooooooooooooo, life came form nothing. thats still abiogenesis.
The idea that life just appeared all by itself seems more far fetched that the idea that life just appeared because someone created it...
and how did this gradual change take place? what made inorganic want to be organic?