The brand value of the word "Twitter" was probably in the billions, and Musk just wiped it away. It was ruined so thoroughly that we can only intelligently talk about it by calling Twitter by its former name because its new name is confusing to even say in conversation.

Twitter's advertising revenue fell off a cliff almost overnight due in no small part to their owner's policy of loudly and publicly attacking individual Twitter advertisers for leaving Twitter.

Twitter had tens of thousands of the most famous celebrities in the world actively participating every day for free, and Musk managed to screw that up in myriad ways, not least of which by falsely labeling them as paid subscribers.

For some godforsaken reason, Twitter's opinion on who and was "notable" or not was a significant status symbol, and Twitter started selling that status symbol for $8/month.

Twitter had a truly impressive internal talent pool, and it's largely gone, ruining their ability to pivot at a time when the whole plan appears to be "wildly pivot."