Good post
@Snarf Zagyg , except for your vile calmuny impugning bards. (I shall meet you at dawn, choose your weapon sir/madam!) Like any event in history, there's many reasons that the trajectory of 4e went as it did (I'm not going to talk about success or failure, I don't think that artificial binary is in any way helpful, a decade and a half plus down the track)\
A few minor comments...
A. At GenCon in August 2007, WoTC botched the rollout of 4e, causing many in the audience to (incorrectly) believe that a computer was required to play the game. This was the start of misconceptions about this edition that the powers that be never really addressed.
I think your excellent chronology/summary maybe somewhat neglects the very widespread lore changes, which started getting soft rolled out in the Grand History of the Realms in 2007, but which came out publicly at a fairly consistent rate with the actual info about the edition rules. Now of course lore quality is a completely subjective matter of individual taste, but in general, people notice changes they dislike more than those they like, and the enormous scope of the changes pretty much guaranteed everyone would be rubbed the wrong way by SOMETHING. Whether it be that your favourite FR deity was now a servant entity of a different god who'd they'd always hated, or whether you didn't like how the elemental planes were mushed together into the Elemental Chaos, or thought the new angels were silly, or were cranky you couldn't play a gnome straight out of the PHB, the 4e lore changes had something to irritate pretty much everyone. There was a whole lot of well-poisoning going on, which made people less inclined to give the edition itself a hearing once it landed. And when you have a game release that changes both the system AND the lore so dramatically - yeah, you're making it very hard for yourself. When you kill so many sacred cows, you're ensuring that pretty much everyone you;re trying to sell to is mourning their own personal Bluebell.
The 4e designers acknowledged that the final push was rushed by directives from the top, which caused them to make the classes too "samey" and left further differentiation on the cutting-room floor. So many parts that could go wrong, did go wrong- key parts of the computer component that was supposed to be rolled out were entrusted to a developer, and that person was unstable and it ended in a horrific tragedy (and also meant no product).
I'd argue these were both not so much a matter of luck, but poor management. Now to be fair, I suspect every edition is rushed to some degree (I know that the 5e weapon table was bodged together last minute without much testing, which is why rapiers are so much better than everything comparable, and why Versatile weapons are pretty rubbish and rarely used), but sometimes you can get away with it and sometimes you can't. Decent management should not be sticking to arbitrary release dates if the coalface people are saying they need more time to bring the product up to scratch.
Similarly, the failure of the computer component (I can with a complete lack of controversy use the word 'failure' here, I think) was not bad luck, it was dreadful management. The fact that the entire project could be ground to a halt by the loss of one person is one thing - this was a VERY well-known project managment problem even back in 2007, and WotC leaving themselves vulnerable to this was pretty much unforgivable. This stuff is my professional wheelhouse, and so it makes me grumpy. Where was management ensuring there was knowledge sharing among the team, or design documentation, etc? Why was the team so under-staffed, for such a major component of a major product release? It's worth remembering that at the time of the murder, the release of 4e wasn't too far in the future, yet once WotC analysed what code they had, they basically gave up on even cobbling a product together. This is at a time when they should have been putting the final touches on and preparing for roll-out, and the codebase was in such a state that they just had to throw it all away. That tells me that even before the murder, the project was waaaaay the hell behind and in deep, deep trouble. Disasters like this don't happen overnight, they take years. This shouldn't have been allowed to happen by competent project management, and it's made worse by the fact that WotC had experienced a very similar failure only a few years before with the 3e e-tools, and apparently had learned nothing from the experience.
If you choose to go swimming wearing platemail and with an anvil tied around your neck, it's not 'bad luck' when you drown.
I. Building on (H), we now know that there were issues flagged by members of the design team, but were ignored. In addition, there were some inexplicable errors (such as the monster hit points).
From memory, this inexplicable error was ... explicked ... by Ben Riggs in one of his recent presentations, in which he said that after MM development was largely complete, a higher-up who'd had no real role in the development of the system took it upon themselves to manually triple the monster hp based on personal vibes. Now WHY this was allowed to happen is pretty inexplicable I admit, but it does rub in the sheer level of dysfunction in the management of the project as a whole.