He went to the realm of the dead, that is, in the Greek, ‘Hades.’ It’s basically saying ‘he died.’ But even if one were to imagine rather materialistically and time-boundedly, Jesus spending 3 days (more like 40 hours over the course of 3 day periods) waiting somewhere to be resurrected, it would not be like the current perception of ‘Hell’ as a place of punishment, but more akin to the Elysian Fields of Greek mythos, thus, the use of ‘Hades.’ Later Christian writing interpreted the ‘time spent there’ as his ‘preaching to the dead’ (all the other humans who’ve predeceased him and are spending time there) and then bringing salvation to the just (now they get to heaven). This is the ‘harrowing’ of ‘hell’ some speak about. ObligiWiki: Harrowing of Hell - Wikipedia
WRT the OP: Let me give you the abridged version…
The theology of the trinity does not come from Jesus saying, “Hey, guys, you know what? I’m pretty sure I’m God himself in the flesh.” It comes from post-resurrectional reflection of the Christian community trying to wrestle with the question: “Just who the heck was he?” And by ‘who’ they meant ‘in essence’, especially when they had to explain Jesus to the Hellenistic (i.e., Greek) culture that was proficient in philosophy. “He’s a god then? What only one God? Then he’s not a god. What? A ‘Son of God’, so then he is a god? Wait, what?”
This development in theology does comes a bit from Jesus who obviously made some sort of statements about he and ‘the Father’ were really close. Add to that:
[ol]
[li]He ‘preached with authority’, i.e., he didn’t quote from the Mosaic Law or the Jewish body of interpreting the Law, but simply said what God wanted, like the prophets did. And prophecy was dead (and outlawed) in Israel for a good half millennium at the time;[/li][li]He performed miracles: exorcising demons, healings, calming storms, walking on water, etc…;[/li][li]He forgave sinners… but only God can do that![/li][li]He rose from the dead;[/li][li]He imparted the Holy Spirit in the form of physical charismatic gifts.[/li][/ol]
And so, the early Church was assured of forgiveness of sins and salvation through their experience of Jesus or his Holy Spirit or the Good News preached about Jesus. But, only God can save. Therefore… OMG, Jesus is God!
That conclusion did not go unchallenged. Some in the community objected and said, well, he’s close to God, or a Son of God, but not God himself.
War ensued, and the trinitarians won.
ObligiWiki: Trinity - Wikipedia