A private equity firm bought them to naked short the stock
You just like throwing around words regardless of meaning?
They owned equity, so they were long, not short. They owned a stake so they weren’t naked.
What they did was a simple extraction of value from something they owned, destroying it. It has nothing to do with short selling, and has nothing to do with manipulation of stock trading (after all, they took it private so that it wouldn’t be publicly traded, so there were no public traders to manipulate).