I have it on good authority that as the roster stands: Darius Garland is basically untouchable. Obviously, very few guys in the league are ever truly untouchable(LeBron, for example). He is the last person the would trade. They would have to get 150% on the dollar, and they did not draft him to trade him.
They also very mcuh do not see Darius Garland as a combo guard. They see Garland as a lead guard, primary handler/lead facilitator. They see Garland directly as a point guard.
You're reading too much into Sexton being here and them liking Sexton.
Their final top 5 board was---from what I heard the week leading up to the draft and after:
TIER
#1- Zion
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TIER
2- Ja Morant
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TIER
3-RJ Barrett
4-Darius Garland
5-DeAndre Hunter
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They had Zion the runaway #1 and top tier. The next tier they for a long time had Ja Morant and RJ Barrett, but over time Barrett dropped down a little bit into the next tier. I wouldn't say there is a huge difference between Morant's tier and the next tier, but they did like Morant a lot. However, a lot of people think Garlands shooting will end up elevating him over Morant long-term.
They were going to take Hunter or Garland, whichever one was left at 5. I think their preference if both remained, which they kinda knew wasn't going to happen, was still Garland over Hunter quite clearly. They did like Hunter quite a lot, and for awhile when it looked like the Lakers were taking Garland pre-AD trade, they did a ton of background on Hunter and came away with him in a tier clearly ahead of Culver, Reddish, etc.
It would be front office malpractice to draft a guy at #5 to trade without a trade literally agreed upon. It is just not something that the Cavs or any team, even the dumb teams, do.