The belief that Jesus descended into hell when he died is based on a misunderstanding of three Bible passages. Here is one of them.
Acts 2:25-27 (New English Translation):
25 For David says about him,
‘I saw the Lord always in front of me, for he is at my right hand so that I will not be shaken.
26 Therefore my heart was glad and my tongue rejoiced; my body also will live in hope,
27 because you will not leave my soul in Hades, nor permit your Holy One to experience decay.
The phrase ‘leave my soul in Hades’ is translated ‘leave my soul in hell’ by some English translations. It is wrong to translate it as ‘hell’. The New English Translation rightly translates it ‘hades’, which is used in the New Testament to refer to the grave. The Hebrew word it is quoting from Psalm 16 is ‘sheol’, which refers to the grave. The footnote on Acts 25:27 in the New English Translation says ‘Often “Hades” is the equivalent of the Hebrew term Sheol, the place of the dead’. The passage therefore simply means that Jesus was not left in the grave by God, he was raised.
Another passage people misunderstand as a reference to Jesus going to hell is this one.
Ephesians 4:9 (New English Translation):
Now what is the meaning of “he ascended,” except that he also descended to the lower regions, namely, the earth?
Some people think that the ‘lower regions’ here is a reference to hell. However, the verse itself tells us that it means ‘the earth’. Like Acts 2:27, it is speaking of Jesus going to the grave after he died. Paul is just taking an Old Testament song (Psalm 68) about the leading of the Israelites from captivity in Egypt and applying it to Christ’s death and resurrection, liberating Christians from fear of death.
The third passage people misunderstand as a reference to Jesus going to hell is this one.
1 Peter 3:18-20 (New English Translation):
18 Because Christ also suffered once for sins, the just for the unjust, to bring you to God, by being put to death in the flesh but by being made alive in the spirit. 19 In it he went and preached to the spirits in prison, 20 after they were disobedient long ago when God patiently waited in the days of Noah as an ark was being constructed. In the ark a few, that is eight souls, were delivered through water.
Some people think that the reference to Christ preaching to ‘spirits in prison’ is a reference to Christ going to hell and preaching to the wicked people there. However, while Jesus was asleep in the grave for those three days he did not do anything. And the grave does not literally have “captives” in it. Since other passages make it clear that Jesus went to the grave when he died (see the other two passages above for examples), many modern commentators understand this to be a reference to ‘Christ’s preaching of repentance through Noah to the unrighteous humans’, as the footnote in the New English Translation puts it.
Peter is also alluding to some Old Testament passages the liberation of captives (Psalm 68:6, 102:20, 107:10, 146:7; Isaiah 42:7, 49:9, 61:1) and showing that Christ liberated those who would believe in him from the “captivity” or “prison” of death and sin, just as God led the Israelites out of Egypt.
There’s also in 1Pe.3:19 a contrast to Jewish teachings outside the Bible which were beginning to trouble Peter’s audience. But that isn’t a major factor in his first letter.