I think the deal was so good for Twitter that it may have been illegal for them not to sell to Musk because their job is to maximize profits or value for the shareholders or whatever. As a publicly traded company, not doing the deal would be choosing to not maximize profits.

Now in hindsight the idiot is killing current stock value, but that still has nothing to do with the shareholders who had stock when Twitter was sold. Those shareholders were thrilled to sell all their stock well above market price. Corporate ethics.