This isn't true in most cases. PE has killed many profitable companies by taking deliberate steps which resulted in the companies directing their incomes to servicing unsustainable debts rather than running or improving the businesses.
For example the eldercare company ManorCare was profitable and successful prior to being bought and destroyed by a PE group. The PE firm loaded ManorCare with the debt that the PE firm used to buy it in the first place and then sold ManorCare's real estate and forced ManorCare to rent it back, causing ManorCare to spend $500 million/year on rent[0]
Forcing companies to take on debt and sell their assets is a standard part of the PE playbook and inevitably ends in the death of the company regardless of how it was performing prior to being taken over.
0: https://skillednursingnews.com/2018/11/washington-post-blame...