However the actual political results were mostly favorable to Republicans. Trump himself popularized the term "deep state" and criticizing it was a key part of his administration's PR.
Russia benefited, not only by getting Republicans in power, but also by embarrassing and casting doubt on U.S. intelligence, a year before Russia's invasion of Crimea. Now in the current Ukraine war it's obvious how vital NATO intelligence is to resisting Russian aggression.
I don't think much actually changed at the NSA or any other agency. Trump didn't actually care about the ethics, he just thought it was some huge, personal injustice that he couldn't command everyone in the executive branch the way he could in his businesses. He didn't even pardon Snowden.
So overall the only changes were political and it all worked out great for Russia. Maybe Russia didn't plan it but they sure benefited from it, with the public and the media doing the heavy lifting. Something to keep in mind the next time some theoretically nonpartisan government scandal appears.
Yes, and it doesn't have to be that dramatic either. Even relatively small shifts in public opinion can matter when it comes to specific areas and/or legislation and/or funding.
In the real world voters are at the mercy of cognitive and other biases, tend to blame the current government no matter what, and a leak's importance depends as much on media attention and trivialities like how close the leak is to an election as it depends on actual merit.
So, even true leaks can be effective tools to remove a government you don't like.
Suppose some government opposes the U.S. in some important way. That government then gets voted out at the next election due to a leak. Would you care if that leak came from a CIA mole? I would. I doubt the CIA would investigate and reveal foreign corruption or illegal overreach purely out of the goodness of its heart.