That's because the possibility of an acquisition is still being priced in. If Twitter announced tomorrow that they were letting Musk off the hook it would take a much greater dive.
That would mean a shrinking possibility of an already bungled acquisition going through is better than the status quo. Seems like Musk has kind of done Twitter a favor by shaking things up. Regardless of the acquisition, it has become clear that the market thinks there is a lot of potential here that's being wasted.
If I made a credible $100B offer for the Campbell Soup company and waived due diligence, the stock price would shoot up, but it's not because they're wasting their potential.
It is objectively better for investors because they get $54.20 a share instead of the current ~$34. It isn't a signal for anything else. Shareholders don't care what happens to Twitter as a company after that, because they have already sold their shares.