There are still pensions and they are also tied to the stock market. Pension funds also have greater influence over CEOs and they need growth every quarter because they are so underfunded (i.e. most pension funds are capitalized based on extremely unreasonable expectations of stock market growth).
So, the reality is that pension funds exert a much greater pressure on CEOs to create short term gains than individual investors who -- incongruously -- take a longer view.
Investors simply do not bid up stock prices for short term gains at the expense of long term. Stock prices are always based on long term expected returns.
It happens that CEOs manipulate the business to show a short term profit at the expense of long term, but if investors find out about it the stock will promptly tank to reflect the long view.
A common related idea is that CEOs gut businesses to satisfy Wall Street. This makes no fiscal sense at all. It can very well be true that Wall Street and CEOs often have conflicting and/or mistaken ideas about which way a business should turn, but it is never about gutting a business.
And yes, if a business can make more money by being "parted out" than as a business, then parting it out makes sense.
So, the reality is that pension funds exert a much greater pressure on CEOs to create short term gains than individual investors who -- incongruously -- take a longer view.