I can't speak to everyone who espouses a very broad set of principles, but I can give a few ideas as to some of the causes.

1. A lot of the people who are in these positions were socially inept growing up. They had no power, they were probably the object of ridicule and they may have been bullied. This applies to the geeks and nerds of Silicon Valley as much as to the Harvey Weinsteins of the world. Suddenly, they have power, they have no accountability and they have beautiful people around them. They can abuse that power to be who they weren't growing up. At the same time, they never came to terms with the underlying power politics of their adolescence, so they sympathize with underdogs and in a very abstract sense speak out for ideas like "social justice" because it strikes a chord. However, in many cases, when presented with concrete people or examples, they're too caught up in themselves to really care. I think this is part of it.

2. A lot of people who have bad intentions are inherently drawn to situations where there is no oversight and so they can do what they want to do largely unpunished. Because the people around them are talking about social justice, sexism, transgender rights, etc., they say the same things regardless of whether or not they believe them to blend in. They also say it to deflect criticism - "How dare you accuse me of sexism? I gave money to that charity for women's empowerment just two months ago!"

3. The absolutely most narcissistic and self-involved of them are probably just virtue signalling. I don't think that needs much of an explanation.