"Not unbalanced on paper" is putting it mildly: on paper it's unbalanced the other way, because I traded the 8th highest scoring RB and the 6th (!) high scoring WR for the 4th highest scoring RB, in a 14-team league, no less.
As you say, there's a few unquantifiable considerations that tilt it back to reasonable, like Hunt's role when Chubb comes back and Jefferson being young, but those kinds of uncertainties are the primary reason any trades happen: one guy bets that a breakout is real (or not), one guy needs depth and the other needs an upgrade, etc. They don't happen if we know someone's a stud now (or not). But really, here's the key, as you put it:
most us have been besieged with injuries to key players
This is exactly right. Adam just lost Beckham, for example, so he had a hole. And lots of people have lost players and desperately need starters. When that happens, and your mid-round fliers have panned out, you've got a lot of options. Adam doesn't care if this makes my team better, and he mostly shouldn't. He just cares if it improves his.
That's the real thing: I've avoided major injuries and the fliers have worked out great. Knock on wood. There but for the grace of God, in fantasy football. But there's no way I'm not cashing in on that good fortune.
(I wouldn't have done it for Hunt and Thielen, BTW. I barely did it as-is. We're one Chubb setback away from this backfiring.)
It's just frustrating. Every year this happens. This is why I've joked multiple times in the past that you must secretly threaten to ban members who reject your trade offers. I've never seen you agree to a trade that I didn't think was heavily weighted in your favor at the time. Of course, not all things play out that way in the long run. I remember being annoyed last year when you traded Kenyan Drake for Kittle (I can't remember if other players were involved or not.) At the time I expected Drake to split carries with David Johnson, but due to inefficiency or injuries or whatever, Drake dominated the backfield and was a top-five back in the second half of the season, so you actually lost that trade since Kittle was banged up a lot, if memory serves correctly.
Earlier last season you traded Ertz for Barkley. Ertz is (or was) a great TE, but typically this is a guy who is drafted in the 4th round at the earliest, and you traded him for an elite RB who was the #1 or #2 overall pick. Barkley was injured at the time, but I think he only missed a couple weeks or something. Of course, Barkley was still hampered by the injury most of the season so he didn't put up crazy numbers until the last month, but it was still one of those WTF are you thinking trades. I remember being especially annoyed about that trade because I had planned on going after Barkley myself and would've given up a whole lot more than an Ertz.
Same applies to this trade. I expect Derrick Henry to be the #1 overall RB by season's end. (Surely Kamara's crazy reception totals won't continue once Michael Thomas returns.) Henry is a durable beast who only gets better as the season progresses. I would've given up a whole lot more for him if I knew he was available, and I'm sure I'm not the only one. Kudos to you for being so aggressive. You're an amazing fantasy player anyway, but your trade acumen exceeds anything I've ever seen. I just wish these other owners would test the market more. At the very least post on here that a player is on the trade block and see what offers they get. I'm not one to propose many trades, and when I do it's typically for a low-tier or bench player who I think has the potential to breakout later in the season. I rarely bother with people's top guys since I assume they're not available.
It's possible that Adam still would've preferred your offer more than anything else he would've received. For Henry, I would've offered him Conner and Evans. On paper, what you gave him is better, but paper is misleading. Jefferson is ranked ahead of Tyreek Hill, for instance, but if I saw a one-for-one trade involving those two in any league, I'd want to smack the person trading away Hill. Chase Claypool is currently ranked as a WR1, but his numbers are inflated from that monster game against Philly. According to the paper scales, you'd be coming out on the losing end if you traded him away for Julio or Golladay or another big name ranked beneath him, but anyone who watches football would know otherwise.
Justin Jefferson is the key to this trade, as Hunt's production, even when Chubb returns, is much easier to forecast. It'll be interesting to watch Jefferson's production the rest of the season. I'm always reluctant to trust rookies or players without a track record, probably to my own detriment, so I'm skeptical that he'll be more than a streaky mid-level WR2, and even that seems like a generous prognostication. Hopefully I'm wrong and you regret this trade and I look like a fool for questioning Adam's fantasy intuition. Henry could tear his ACL next weekend for all we know. For now, though, I'd be shocked if you didn't perform a victory dance once the trade was accepted. I'll be checking the hidden cameras I've set up throughout your house to see if I'm right.