Did God leave all mankind to perish in the estate of sin and misery?
God having, out of his mere good pleasure, from all eternity, elected some to everlasting life, did enter into a covenant of grace, to deliver them out of the estate of sin and misery, and to bring them into an estate of salvation by a Redeemer.
Ephesians 1:3-4 (ESV)
Blessed be the God and Father of our Lord Jesus Christ, who has blessed us in Christ with every spiritual blessing in the heavenly places, even as he chose us in him before the foundation of the world, that we should be holy and blameless before him.
The God and Father of our Lord Jesus Christ, has blessed us in Christ, choosing all the believing in Christ before the foundation of the world; this is true election and predestination.
Romans 3:21-22 (ESV)
But now the righteousness of God has been manifested apart from the law, although the Law and the Prophets bear witness to it— the righteousness of God through faith in Jesus Christ for all who believe.
The Lord God has declared the believing in Jesus Christ righteous. This is a covenant of grace, because it is not by keeping the law that we are righteous, but it is through faith in Jesus Christ for all who believe.