Say what you will about Twitter, but is a globally distributed database with trillions of entries, which has to add and sort and display billions of those entries in real-time for 100+ million daily active users. And it has to resist nation-state bad actors doing everything they can to corrupt it.
As a result, I would guess a lot of Twitter's engineers are working on infrastructure, internal tooling, and moderation.
Regarding your example, doubling the size of a tweet, that was probably more work than one dev writing ALTER TABLE tweets MODIFY tweet_text VARCHAR(280). In fact, I don't know if you were around 20 years ago or so, but there was a similarly scoped project to double the number of digits we were storing the year in. ;)
Would you want to date someone who seemed desperate to get into a relationship? Who seemed like they were having trouble getting a relationship at all, let alone a good healthy one? Same principle.
As a result, I would guess a lot of Twitter's engineers are working on infrastructure, internal tooling, and moderation.
Regarding your example, doubling the size of a tweet, that was probably more work than one dev writing ALTER TABLE tweets MODIFY tweet_text VARCHAR(280). In fact, I don't know if you were around 20 years ago or so, but there was a similarly scoped project to double the number of digits we were storing the year in. ;)