After making a career out of exposing the most powerful people in the world, it would make sense that someone might want to tarnish Greenwald's reputation. Governments and intelligence agencies, from Brazil and Israel to the U.S. and Ukraine, have plenty of motive here. That doesn't mean this was a government operation, but speaking truth to power often comes with dangerous pushback.
Greenwald may have been a threat to some in the past, but in recent years, he's been nothing more than a Trump apologist pushing conspiracy theories about the media industry he left. Whoever leaked these videos clearly doesn't respect Greenwald, but that could be anyone given the ex-Pulitzer Prize winner's fall from grace.