I had this conversation the other day. HR exists to protect the firm, if that involves sweeping things under the rug, disparaging victims, or enabling illegal behavior by high performers, they will, and historically have, done it.
HR departments are intended to protect the company from liability. Generally speaking, they do that by taking standardized actions regarding harassment claims because otherwise they open the company up to lawsuits and negative PR.
Basically, it's irrational to try to cover up or ignore harassment in the vast majority of cases. Which is why HR is a perfectly decent solution for most of these issues, and we only hear about a few outliers in the media / law suits.
HR does what their bosses tell them to. If the company culture is more conductive to sweeping the transgressions of a director under the rug, then to firing them, then HR will do just that. After all, the director/c-level/partner is making them millions of dollars, and well, most people won't file a lawsuit over a few dozen inappropriate comments or invitations to a hotel room. (Good luck getting a reference after you do.)
Engineers are also supposed to build bug-free software, but when your boss tells you to ship the product, you're going to ship it. If the company gets sued because your product has bugs, you're not going to be personally liable.
If that's true, which it may well be in that case, I'd say that Uber is an exception to the rule and the HR department was simply run in a (frankly) idiotic and irrational manner.
HR departments are intended to protect the company from liability. Generally speaking, they do that by taking standardized actions regarding harassment claims because otherwise they open the company up to lawsuits and negative PR. (see Uber)
Most company HR departments take harassment VERY seriously for this reason, especially if the harassment was written in black and white, such as Susan Fowler claims her harassment was.