In the 1st letter of Peter we find a section in which it is stated that Christ preached to spirits who are in prison. Is this about people? Did Christ preach the gospel to the dead in the realm of the dead after His resurrection, as one sometimes reads here, or is it about something else? Below first the verses in question from 1 Peter.
1 Peter 3
18 …He (=Christ), who was put to death in the flesh, but made alive in the spirit,
19 in whom also He went and preached to the spirits in prison,
20 who sometime were disobedient, when the longsuffering of God waited in the days of Noah, while the ark was being prepared, in which a few, that is, eight souls, were saved through water.
people are not spirits
It should be clear when reading this passage that it is about spirits, that is to say: spiritual beings. We do not read anywhere in Scripture that people are referred to as spirits. We do read that they can be possessed by an unclean spirit (see for example Mark 5:2).
Which spirits these “spirits in prison” are that are mentioned in 1 Peter 3:19, is clear from the context. They are disobedient spirits from the days of Noah. This can only refer to one group of beings and that is those who are called sons of God in Gen. 6:2. They mixed with people and thus giants were created (NBG and Statenvertaling), in Hebrew: Nephilim. These events appear to be the direct cause of the flood, as we find described in the first verses of Genesis 6. Jude also refers to this in his letter.
Jude
6 And the angels, which were unfaithful to their first estate, but left their own habitation, He hath reserved in chains, which cannot be seen, under darkness unto the judgment of the great day.
angels
They are angels (lit: messengers) who became unfaithful to their origin. That is to say: they have gone after other flesh (Jude :7) and have mixed with people. Peter also speaks about this in his second letter:
2 Peter 2
4 For if God did not spare angels when they sinned, but cast them with cords of darkness into the abyss and delivered them to be reserved for judgment…
reserved
These spiritual beings are reserved by God in the abyss (Greek: Tartarus) until the day of judgment. In 1 Peter 3 Peter declares that Christ was killed and made alive and that after His resurrection He proclaimed to these spiritual beings in Tartarus, their prison until the day of judgment.
no people in the afterlife
What Peter writes therefore has nothing to do with the conclusions that are sometimes drawn from these passages. This is not about Christ proclaiming His victory to people in the afterlife, hell, or anything like that. Peter is writing about Christ proclaiming victory to spirit beings who are being kept in Tartarus until the day of judgment.