There are multiple factors to blame if we're going to do a full accounting of what killed traditional TV. I agree that greed is definitely one of them. Overpriced cable/satellite bills, extreme and intrusive levels of advertising, etc. It simultaneously got more expensive and more monetized while being less worth it. You could argue that the introduction of ads to cable TV, even though the original premise of paying for cable was that you were paying to avoid advertising, was the "original sin" that doomed the future of television.
I posted this theory a few months ago, and I still believe it: I also think the historic laziness of American TV presentation is a big part of it. Compared to other countries that had idents, live announcers (sometimes on camera a la MTV's VJs) and all sorts of other extras that made TV feel like a big event, the presentation of American TV has always been minimalist and impersonal. In the long run, I think it's cost the networks dearly since they never developed the same brand loyalty as, say, the BBC that might have helped them hold out for longer against streaming and make the eventual transition more graceful.
That laziness and lack of ambition extended to the programming, too. Networks started cancelling shows before they could even find an audience because it was safer to just recycle the same formats over and over again. Cable networks that started out with specific visions all drifted into being the same general-entertainment channels with the same programming before decaying into a worse version of Netflix binge-watching with ads every five minutes. And of course, the lack of local programming besides news doesn't help either. Most broadcast stations' schedules are full of syndicated crap that clearly nobody misses on streaming.
Streaming is already heading in the same direction. It's becoming more expensive and fragmented, more encroached with advertising, too quick to cancel shows, and so on. It shows that the real problem was never traditional TV itself, it was the corporations behind it who simply can't help themselves.