They fail because they need to become billion dollar behemoths to support the VC funding they've gotten. But plenty (not all though) of them could be profitable if they were ran as a "lifestyle" business.
With the debt that Elon has saddled them with I doubt they will ever be profitable again without declaring bankruptcy.
Without the $760M settlement, they'd have made about $270M in 2021[1].
[1] "2021 operating loss of $493 million, or an operating margin of -10%, includes a one-time litigation-related net charge of $766 million" - https://www.prnewswire.com/news-releases/twitter-announces-f...