Do we sin because we are sinners or we are sinners because we sin?
We are born with a sinful nature and as such, we sin. It's just part of what we are as fallen human beings. We are born sinners and sin is like a second nature in us.
We are not sinners because we sin. We would still be sinners, even if we would never sin. Our very existence is sinful. Sin is a manifestation of our nature.
Jesus was not born with a sinful nature, and as such, He could not sin. He could be tempted, yes, like any of us. But He could never fall into temptation, because it was against his sinless nature.