✔ 最佳答案
In Genesis 6:3 God made what the lifespan of man in the flesh should be.
So all people who where born after this had a generation of 120 years.
Those such as Adam who were born before did fall under this, thus the longer life.
Genesis 6:3 “And the LORD said, My spirit shall not always strive with man, for that he also is flesh: yet his days shall be an hundred and twenty years.”