Did God leave all mankind to perish in a state of sin and misery?
No, God purposed to save His people by sending a Redeemer.
Ephesians 1:4-5 Just as He chose us in Him before the foundation of the world, that we should be holy and blameless before Him. In love He predestined us to adoption as sons through Jesus Christ to Himself, according to the kind intention of His will.