I think OP is referring to something besides VC, so I'll address the general case of an outside entity investing money in an existing business and using that leverage to make changes. There are a lot of types of entities who do that, and getting into the details of each one is beyond the scope of this post. However, I will focus on the "negative" cases.
First, these outside change agents typically have a thesis that existing leadership has been mismanaging the assets of its shareholders (everything from officers of the company to 401ks amd pensions) in some way. Another way to say that is that they believe the company is, or soon will be, in trouble. This is typically through inefficiency (eg keeping multiple headquarters or outdated operational methodologies), lack of vision (eg erratic or nonexistent strategic moves have left the company wandering), or a structural disadvantage (eg being spread across too many unrelated business lines and performing poorly due to lack of focus).
One thing that should be clear is that these are not easy problems to solve. They involve massive change to bring a company from danger to competitiveness. This is not comfortable for anyone involved, but in many cases the options are to go through traumatic change or go out of business.
Oftentimes companies are broken up and pieces sold to more innovative or effective firms. Positions that dont add value to the enterprise are laid off. Processes are radically changed, and the people responsible for the things that were failing before dont usually enjoy it.
That is the psychology. People who are laid off never think that it had to be that way, and they always think it was shortsighted on the part of the acquirer. People never think their division should have been sold, they worked hard and it hurts to be "discarded" and absorbed. Accepting dramatic process changes is difficult. These are the people you hear from. Sometimes they are right, more often they are not. If they were right, it would be the PE sector failing, because it is subject to the same logic as industry. Plights sell newspapers; explanations of economic rationality do not.
Moving to editorialism now: there is a strong current of "science denial" in our country (and most others) when it comes to business and economics. Good people can fail and good companies can fail. When you don't allow regular forest fires to clear the fuel load, you get massive, uncontrollable fires. Likewise, detritus builds up when you don't allow some level of turmoil in the capital and business sector.
Like democracy in politics, capitalism is the worst economic system, other than all the other systems that have been tried.
As someone who has some experience in the financial side of business, I have a healthy skepticism towards second order+ securitization and certain other forms of financial engineering. I think that skepticism is, in fact, healthy. But at the same time, our financial sector is a critical enabler of growth and our unprecedented standard of living.
