I'm not 'in the know' by any means, but for my own sanity I thought I'd try to summarise my understanding how we'd got into this current situation.
Please let me know if I've got any of this wrong, or have said anything inaccurate
I believe DC bought the club with the idea of spending a bit of money and being a hero.
He didn't come with the football contacts or experience, so needed advisors from within the game - enter Doyen Sports, in particular Paxo. In terms of player signings, this seemed to work out quite well at first (I understand we got Lucas Joao from our link with Paxo), but there have been some not so good signings since. Whether this is down to bad judgement or people acting in self interest, I don't know. A quick Google search reveals a lot of negative articles about Doyen Sport and their subsidiaries, some of which merely highlight that obnoxious, brash young men work in the football agent business, which however distasteful is hardly news, and is not illegal.
None of this really matters until you factor in FFP. Previously, if you sign a dud on big wages, then you just sign another to replace him, no problem if you've got deep pockets. This is where DC's naivity actually starts to damage the club, and brings into question the quality of his advisors. He says the EFL changed the rules, but he also admits that we missed the limits by an eight figure sum i.e. at least £10m. So regardless of whether goal posts moved or not we clearly "gambled" on getting to the premier league, and lost.
Is this unforgivable? I don't think so. Most clubs who get to the premier league do so on the back of a gamble, where there are inevitably winners and losers, decided over 90 mins at Wembley.
I think DC underestimated the EFL and tried to game the system with some questionable income streams. He didn't reckon on the EFL rejecting this (perhaps the "rule change" he alluded to?) and then found himself stuck in the FFP trap which means those duds on high wages are now restricting transfer activity to the point where Joey Pelupessy is the best we can get. In hindsight the Jordan Rhodes signing looks like an incredible indulgence, but maybe DC didn't realise how much of a gamble he was taking at the time? Money is what DC brings to the table, and when he can't spend it, he doesn't bring much else.
At this point most would expect him to be questioning the wisdom of his advisors. We then have the George Hirst saga. Whilst his stock has decreased since his move to Belgium, he was seen as our best young prospect at the time, and let's not pretend his surname is irrelevant. With Doyen both representing Hirst and advising DC, the fact that a star of the England youth team and son of a Wednesday legend left in the way he did left a bitter taste in the mouth for many, a slap in the face to fans (and DC) relishing the idea of seeing another Hirst in the no.9 shirt. Fairy tale stuff.
Finally we have Jos, another Paxo deal. Out of work for two years, on the brink of retirement when he gets the call from Sheffield Wednesday. By any standards he has not been a success. Senior pro's frozen out, worst defensive record in the league, different team different system every week. Maybe not all Jos's fault, but all happened on his watch. Now criticising the players in public, a well worn path to getting fired, but not according to DC, again questioning the judgement of him and his advisors.
Add to the mix that the most inventive way of increasing revenue streams seems to be increasing ticket prices and the fact that most of these inflated tickets were sold to fans without informing them that we were under a transfer embargo, and it's easy to see why some have had enough of DC.
Then things escalate. Every word from DC is scrutinised to the point where a casual remark about the Jordan Rhodes signing becomes "DC blaming the fans" for months afterwards, "fans" send abuse to his family on social media, every move is criticised - he stubborn/he's weak, he's not being honest/he's being indiscrete, he should say more/he should say less etc. Thin skinned fans and a thin skinned chairman getting increasingly offended by each other ad infinitum, both convinced they're in the right, both blind to the others point of view.
If DC does now sell up, I for one think it'll be a shame. I genuinely think he came to try and build something and has been thwarted by naivity, poor advice and the bad timing of FFP. All of which could be overcome given time and a bit of humility.
If the next guy knows football inside out, but can't or won't pay £20k a week for decent footballers, then all the time and humility in the world won't solve that problem.