In the beginning, God told Adam to do just one thing and he disobeyed.
Adam had walked with God and was given all things freely but he still disobeyed just that one commandment “Do not eat from the tree of knowledge of good/evil”
This is because when the commandment comes, sin is made alive as Paul explained for those under the law:

Romans 7:9 “Once I was alive apart from the law; but when the commandment came, sin sprang to life and I died.”

That shows that man is incapable of pleasing God by works.
It is not as if Adam was worse than all of us.
Adam was just like you and me – a mere human being who could not please God by his own willpower.
Every human being would have failed in the place of Adam.
That is why Paul said this:

Romans 3 “10 As it is written: “There is NO ONE righteous, not even one; there is no one who understands; there is no one who seeks God. 12 All have turned away, they have together become worthless; there is no one who does good, not even one.”

Romans 5 “12 Therefore, just as sin entered the world through one man, and death through sin, and in this way death came to all people, because ALL sinned—”

We all sin, just like Adam.
Humanity cannot please God by their works.
This is why Israel was given 613 commandments and yet they failed. The Law was given to show that nobody is righteous, not even one.

Romans 3 “19 Now we know that whatever the law says, it says to those who are under the law, so that every mouth may be silenced and the whole world held accountable to God. 20 Therefore no one will be declared righteous in God’s sight by the works of the law; rather, through the law we become conscious of our sin.”

So then God made a NEW COVENANT.
God became a man Himself through Jesus Christ.
God came in the flesh and He obeyed all the commandments
so that Righteousness is given to all who believe.

Romans 3 “21 But now apart from the law the righteousness of God has been made known, to which the Law and the Prophets testify. 22 This righteousness is given through faith in Jesus Christ to all who believe. There is no difference between Jew and Gentile, 23 for all have sinned and fall short of the glory of God, 24 and all are justified freely by his grace through the redemption that came by Christ Jesus. 25 God presented Christ as a sacrifice of atonement, through the shedding of his blood—to be received by faith.”

What does it mean to believe?
It means to trust in Jesus and not in our efforts.

Romans 4 “4 Now to the one who works, wages are not credited as a gift but as an obligation. 5 However, to the one who does not work but trusts God who justifies the ungodly, their faith is credited as righteousness….for us who believe in him who raised Jesus our Lord from the dead. 25 He was delivered over to death for our sins and was raised to life for our justification.”

Believers are righteous because Jesus Christ obeyed everything!

Romans 5:19 “For just as through the disobedience of the one man the many were made sinners, so also through the obedience of the one man the many will be made righteous.”

It is not by our efforts but by HIS GRACE & MERCY.

Romans 9:16 “It does not, therefore, depend on human desire or effort, but on God’s mercy.”

Romans 11:6 “And if by grace, then it cannot be based on works;”

It is only by the GRACE of God that we can even believe!

Acts 16 “The Lord opened her heart to respond to Paul’s message.”

We believe because God attracted us to Jesus and He chose us.

John 6:44 “No one can come to me unless the Father who sent me draws them, and I will raise them up at the last day.”

John 15:16 “You did not choose me, but I chose you”

John 10 “28 I give them eternal life, and they shall never perish; no one will snatch them out of my hand. 29 My Father, who has given them to me, is greater than all; no one can snatch them out of my Father’s hand. 30 I and the Father are one.””