Private equity paid the original shareholders for Toys 'R' Us. The limited partners in this fund (and creditors) lost a lot. The managers extracted their management fee, but that's basically only salaries. Good salaries, but none of the 20% of the upside that makes people in PE rich.
I agree that workers are left out. Employees in private-equity acquired companies should get (a) stock (or better yet, an interest in the diversified fund) and/or (b) enhanced downside protection (e.g. longer or bigger unemployment benefits, paid for by the private equity fund). But in this specific case, employees didn't turn out that much more badly than they would have otherwise. (For those who might have lost their jobs in the next recession, their lot was arguably improved.)