Your title is, “Risen Christ Preached to the Spirits in Prison” —but Christ had not yet “risen” when he went down below to preach to the spirits there.
Here is my current understanding on the topic:
In Christian theology, the Harrowing of Hell (Latin: Descensus Christi ad Inferos, “the descent of Christ into Hell”) is the triumphant descent of Christ into Hell (or Hades) between the time of his Crucifixion and his Resurrection when he brought salvation to all of the righteous who had died since the beginning of the world.
Apparently, the abode of the dead below, known as “Sheol” in Hebrew, and “Hades” in Greek, used to have two compartments, one for the righteous dead known as “Paradise” or “Abraham’s bosom,” and one for the sinful dead.
However, after Christ’s perfect Blood was shed, the righteous dead could now go up to heaven. So when Christ ascended back to heaven, the Paradise compartment went up with him, and was relocated above, becoming a temporal subsection of heaven. (Regarding these distinctions, consider 1 Sam. 28:11-19, Luke 16:19-31, 23:40-43; Ephesians 4:8; 2 Corinthians 12:2-4.)
After he died, Christ went down below to Sheol in spirit, and apparently visited both compartments:
He “proclaimed” to the sinful dead in their compartment of torment (1 Peter 3:19-20)—and there they will remain until Judgment and their transfer to the remedial lake of fire; whereas,
He “preached the gospel” to righteous dead in their “Paradise” compartment known as “Abraham’s bosom” (1 Peter 4:6), and they subsequently followed Christ to heaven at his ascension (Eph. 4:8), because they had been “prisoners of HOPE” (Zech. 9:9-12).
Regarding Christ’s visit below to the sinful dead:
1 Peter 3:18-21 (ESV)
18 For Christ also suffered once for sins, the righteous for the unrighteous, that he might bring us to God, being put to death in the flesh but made alive in the spirit,
19 in which he went and PROCLAIMED [kēryssō] to the spirits in prison,
20 because they formerly DID NOT OBEY, when God’s patience waited in the days of Noah, while the ark was being prepared, in which a few, that is, eight persons, were brought safely through water.
21 Baptism, which corresponds to this, now saves you, not as a removal of dirt from the body but as an appeal to God for a good conscience, through the resurrection of Jesus Christ,
Regarding Christ’s visit below to the righteous dead:
1 Peter 4:4-7 (ESV)
4 With respect to this they are surprised when you do not join them in the same flood of debauchery, and they malign you;
5 but they will give account to him who is ready to judge the living and the dead.
6 For THIS IS WHY the GOSPEL was preached [euaggelizō, to bring good news] even to those who are dead, that though judged in the flesh the way people are, they might live in the spirit the way God does.
7 The end of all things is at hand; therefore be self-controlled and sober-minded for the sake of your prayers.
Note: I think Peter’s reference to those who died in the Flood of Noah, does not limit Christ’s visit to the sinful dead to only those that died in that catastrophe. Rather, Peter referenced them specifically because he was also setting up a connection to WATER BAPTISM, the reality of suffering, and the need for self-control in a corrupt world.