BlackRock is the largest owner of 330 of the S&P500 companies. Similar story for most other markets. So them pushing a somewhat green agenda is actually a big deal and very usefull.
i can't remember the details because i'm poor but they manage other peoples money so a lot of people who care about the environment have money in a 401k or something which means blackrock control the shares they own and vote in shareholder meetings for whatever's best for rich people - there's a way to be more proactive by registering your ownership yourself but i have no idea what it involves.