140 is more than just aesthetics. The enforced brevity is what makes so many people regular readers of a tweeter that would not be regular readers of a blogger or of a serial essayist. If Trump pushed out five ten minute reads per day, only people paid to condense them into shorter forms would read them (journalists and analysts). And that's supposedly the most important person in the world, the impact of a switch to longer forms would be even bigger for other Twitter celebrities. The brevity vs. depth tradeoff is also a tradeoff between reach and depth.
On a certain level of abstraction, Twitter's achievement is an implicit contract between writer and reader that promises a certain standardized answer to the brevity vs depth question that greatly helps brevity to fulfill its potential of generating reach. Tweaking that contract, even by a mere 140 characters is huge (Twitter, of all entities, should know how important 140 characters can be).
On a certain level of abstraction, Twitter's achievement is an implicit contract between writer and reader that promises a certain standardized answer to the brevity vs depth question that greatly helps brevity to fulfill its potential of generating reach. Tweaking that contract, even by a mere 140 characters is huge (Twitter, of all entities, should know how important 140 characters can be).