The Musk effect hurt Twitter before he even completed his purchase. Investors traded shares for under $40 before he made his interest known in April. Analysts think that they would have fallen below $30 if Musk never got involved. But he did and they inflated to above $50 per share as he overpaid for the social network.
It was stupid of Musk to involve himself in this in the first place but he backed himself into a corner. After he withdrew a bid for the company he had a legal battle with the company. Then he changed his mind and agreed to buy it because he knew that he would lose the case. No wonder he doesn’t care about ruining it (via Fortune).