I don’t remember who stated this but basically there is this thought that Musk was in fact mad about how on Twitter the “common man” could indeed vocally and effectively share their disagreement with his decisions.
It also might have been an impulsive decision to become relevant in “new tech” at the same time (why would he care so much about this, boredom?). Ultimately he probably just wanted to get out of that impulsive deal again though but it was too late.
Lastly he probably also had/has some WeChat ambitions.
We can see how most of these potential goals are now falling apart spectacularly due to extreme unreflected and unchecked ego.
He seems to have succeeded in the first case though, the “moderated”/“mostly sane”(?) free speech “town square” basically destroyed and replaced by an increasingly irrelevant echo chamber for his greater brand.