This is a strawman because no one has claimed that a CEO must focus on short-term shareholder profit.
The point is that the CEO works for the owners of the company. (In a publicly traded company that's typically shareholders represented by a board.) To keep their job the CEO just needs to be able to convince the owner(s) that they're making the right decisions.
In the case of Apple, most owners (shareholders) trusted Steve Jobs' decision to cannibalize existing product lines with new ones.
In the case of Twitter, I am skeptical that the owners would have trusted Jack enough to let him transition Twitter to an open protocol without some kind of long-term monetization plan.
No it isn't. The claim is "A CEO is just an employee, paid by the shareholders to do the job shareholders want him to do." That claim lets four words, "the job chareholders want," work pretty hard. Could mean anything. Could be "run great shareholder meetings with lots of swag" or it could mean "do something that we can't imagine ourselves because otherwise we'd do it instead of investing here."
In TFA Dorsey briefly describes his vision of what to do after taking Twitter private. He is speaking to who would become the effective owners. In the car repair analogy it is as if a rental van was in a fender bender. The rental co can get it fixed with a normal bodyshop or has an option to sell it.
Down the street there is a body shop with a vision. The owner of that shop knows a lady who wants to wants to start a food van and is telling her, "I know a dinged rental van you can get at a discount and when we finish conversion it will look better than new."
When you (sarcastically?) said "That's right, CEO needs to focus on those quarterly numbers" it seemed like you were implying that this was someone's argument.
As no one is making this argument, it's rather hard to continue the discussion past that point but I will try. I agree that the CEO can actively seek out new owners that more closely match the CEO's vision, but even then they are working for the existing owners (who must agree to sell) until it is sold, at which point they will be working for the new owners.
The point is that the CEO works for the owners of the company. (In a publicly traded company that's typically shareholders represented by a board.) To keep their job the CEO just needs to be able to convince the owner(s) that they're making the right decisions.
In the case of Apple, most owners (shareholders) trusted Steve Jobs' decision to cannibalize existing product lines with new ones.
In the case of Twitter, I am skeptical that the owners would have trusted Jack enough to let him transition Twitter to an open protocol without some kind of long-term monetization plan.