I think a bigger key for Darnold and Baker is that their lines are also very good, those guys played places with weapons before and were terrible. Seattle's line is less good, but they have had a big jump with the same personnel, that you can probably attribute to the new coaching staff.
When did those guys play with weapons like they have now, and were terrible? In the seasons Darnold played significant time, these were the leading receivers:
Darnold
2018: Robbie Chosen, Chris Herndon, Quincy Enunwa
2019: Crowder, Chosen and the corpse of Demaryius Thomas (RIP)
2020: Crowder, Berrios, Herndon
2021: He went to Carolina, the team started 3-0 Darnold had a 99 QBR, almost 900 yards, 3tds, 1int), and then CMC got hurt and they lost 4 of their next 5. Then CMC came back for a game and Darnold got benched/hurt, and they went 0-5 under Cam Newton.
Mayfield
2018: Jarvis Landry, Njoku, Calloway
2019: OBJ, Landry
2020: OBJ, Landry, new head coach, Chubb, Kareem Hunt (best season of Mayfield's career)
2021: Landry/OBJ/Hunt play a total of 26 games, and Mayfield sucks again
2022: He spends parts of the season with 2 different teams after their QB's went down
2023: Goes to TB and puts up 4,000 yards, 26tds, 10ints
Geno Smith started 5 games in 6 years before Seattle brought him off their bench when they dumped Wilson, threw him out there with Metcalf/Lockett/Walker and he went crazy, leading the NFL in comp% and putting up a 100+ rating. That was just two years ago with the same personnel they have now, so this season is a jump from last season, but not a big jump for what they've done, and as you point out, I think last season had more to do with locker room/coaching issues than anything else.
Miami has a lot of weapons, but we're also comparing apples and hand grenades when we talk about Baker/Darnold/Geno and those guys playing with weapons vs. Tyler Huntley or Skylar Thompson. Baker was the #1 overall pick, Darnold was the #3 overall pick and Geno was 39th overall. They are talented QB's who weren't put in good positions at all, whereas Skylar Thompson was a 7th rounder taken 247th overall and Huntley was an undrafted free agent who Baltimore brought in assuming he could just run like Lamar when/if Lamar got hurt.
I'm not saying lines don't matter. Far from it. I don't think anybody could succeed behind this Pats offensive line. Been saying that for 3 years now, but you also need weapons. Ground and pound and keep your QB upright for a couple hundred yards isn't a strategy. You have to be able to stretch the field, you have to have at least a couple of guys who can turn a 10 yard gain into a 30-40 yarder on occasion. We've got none of that and haven't for years, and now we have a really fucking shitty line (maybe the worst I've ever seen) to go along with it. The good news is that if Drake Maye can show literally anything with this group, it would be pretty strong evidence that he's the real deal. That's the only hope left for this season (well, aside from losing games and getting better draft pick spots as a result)