I only say failed so much as they were earlier to the market but they're not the reason why streamers are taking off. The streaming devices are around ~39% of the market of the streaming market as a whole, and Roku has almost half of that. Roku marketed to cord-cutters, people who want alternative ways to get their television. Apple seemed content to sell to their current customers and provided an expensive box that didn't really offer that much. Google pimped Google TV and watch those devices fail one after another, Vizo Co Star anyone? And then in comes Amazon with rather impressive specs and suddenly Roku is is trying to compete against what was, at the time, a better hardware device, Apple ups his game and Google re-enters.
What's my point in all this? Amazon is one of the leaders, and whether or not other devices catch-up or exceed what they offer to different groups, the Echo is at the forefront. No one was really paying attention to these things until this third parties like Roku and Amazon started doing what they're doing.
I always recommend the Roku route myself to anyone not in a paywall already. But Echo is wanted.
I have 1 Echo, 1 Echo dot, One Fire Stick, Two Amazon TVs, 2 Roku devices. I returned POS that was the original Chromecast. I also had the Vizio co-star which had great specs, ran like an oven and was generally awful all around.