We all watched this too long.
There are many reasons to can Hahn. Here is one, the C position as a whole.
Let's look at the last few years of Hahn's performance re: the C position:
a) Letting Narvaez go and develop into a better player elsewhere;
b) Drafting Collins in the first round at all (and watching how MiLB Rule-5ers Yerminator, Narvaez, late rounders like Kevan Smith and especially Seby Zavala all develop into comparable or better players as his 1st rounder;
c) Insisting over the years like everyone else in the inept Sox FO that Collins was a C when all of baseball insisted he wasn't, all the while watching his trade value gradually become lower and lower over time until he got into the same situtation of most bad Sox FO high round picks i.e. you might as well hope for growth because the trade value is zero;
d) Signing Grandal when McCann was a far superior defensive/pitcher's C *and* when McCann was available to be signed to an extension which would have been a shorter deal for much less money at the time;
e) Never actually knowing that Grandal was a shitty defensive player anyway while most other people seemed to, and generally and miserably failing to recognize that the proper way to augment an exciting (if threatening to be one-dimensional) young offense is to add pitching and defense to it, not adding more offense at the expense of pitching and defense;
f) Collins for McGuire: finally, at long last, Hahn salvages some of Collins value and acquires 4+ years of controllable Reese McGuire, a quality lefty platoon backup C that teams like the Padres and Guardians usually acquire and hang on to, but he just can't leave well enough alone, so Hahn has to trade Reese for Diekman.
First, it should be noted that Hahn only got McGuire because the Jays were forced to cut their extra 3rd C because their FO is full of people who maybe are "too good" for their jobs, and have "too much depth," unlike the Sox who generally have needs because they are stupid and can't admirably fill them at all.
So Hahn of course then takes 4+ years of a lefty-hitting cheap platoon C in McGuire, who is way better than 1st rounder Zack Collins has ever been, and trades him for an older 2nd pen lefty in Diekman who is under shorter control but who is owed millions and cannot be cut without freely unlike McGuire. But the real kicker here is we already had 5 years control of Tanner Banks as a second lefty -- and a considerably more versatile one at that -- and so there was really no point to acquire Diekman at all, even at the time. Hahn was "building quality depth" by taking that cheap long-term potential part-solution and exchanging it for essentially an improvement over Tanner Banks -- hey, would the decision makers with Dodgers or Rays or CLE even think Diekman is better than Banks at all? prolly not IMO -- and so Hahn sends Banks down to bring over his new money-making gas over from Boston, who was happy for the free cheese. This is how Rick Hahn "spends money," "uses trade capital," and "builds quality depth."
Suffice it to say, the Rays, Dodgers, Yankees, etc. don't make real long habits of operating in these "White Sox ways." Just look at what Hahn has had to work with (Rule-5 good players, Reese salvaged for Collins aka Nothing, McCann for literally nothing, etc.) and then look at what he's ended up with: really expensive and shitty defense at C in the form of a guy who physically has deteriorated exactly as expected and is now (as should have been expected) a sunk cost albatross platoon 1B/DH (again).
