A small short-lived productivity increase, followed by a mad rush of other services trying to spin up (or scale up if already running) and piling lots of man-hours into advertising themselves as the best replacement. Also many miles of column-space pontificating on the whys/wherefores, and a few people will try to sue because there was one little bit of irreplaceable information on there that is vital to them and they didn't have backed up elsewhere. Other than that, little or nothing of long-lasting consequence I expect.

Users'd probably just join Reddit. It's full of snark and outrage too

Elon would make his own Twitter called Doge-r, and a company that developed it and also did construction, so he could have dump trucks called Dogers (as in bulldozer), jokes about "taking a dump", etc

No hate to any of the engineers there, but honestly, it would be a net positive for society.

The level of vitriol, hate, and performative outrage has reached up to the gods on Twitter. The valuable signal that comes out has long been overwhelmed by the noise.

There are other platforms that largely fulfill the same purpose.

Journalists might start engaging with the wider public again rather than constructing their stories from within an echo chamber.

As tempting it is to write world peace and leave, that wouldn't be true.

Biggest unofficial support channel would be closed.

Also my large smut collection would be inaccessible.

Mr Musk buying it for a cheaper price