http://www.theverge.com/2017/2/19/14664474/uber-sexism-alleg...
I noted it solely because it's unusual.
It is true that if you are going to _attempt_ to change a culture, it must be motivated from top-down. However, placing that responsibility on the CEO alone is misunderstanding of how culture works.
It's a little akin to saying that culture is the President's responsibility. No, it's everyone's responsibility, and if you want to change it, the influential people in your org (country) must lead and reinforce that change.
The best you can say is that the founder(s) laid the groundwork for the culture. As with anything, changing the foundation later is extremely difficult.
That's what the research says, anyhow. I studied this briefly during my undergrad.
After a certain size the only way to make a change stick is get rid of people that disagree. Or, you can wait for pressure to wear those people down over... A period of years.
If Ubers culture is really this toxic the only way to fix it would be replacement of a fair amount of leadship in the company.
To a point, but when HR gets involved and does not help, that IMHO is often due to the upper leadership being a big part of the problem. I've seen HR blow off inappropriate behavior when the CEO does or is okay with it.