Whether because of mighty marketing campaigns, years' worth of buildup or just a game's story going in a certain direction, the game industry has a real love/hate relationship with hype and expectation.
To some degree, the very notion of amping things up is just part n' parcel of working in the medium. Honestly, it's not until you start dissecting the way movies and TV marketing works that you realise how secretive and "controlled" the messaging of any game's release is.
Look at No Man's Sky, for example. Until launch day the majority of consumers had no idea what they were buying, and that extends into every "exclusive screenshot", every conceptual trailer, every early beta. Everything that happens before you can make a judgement call yourself.
With so much manufactured deception happening - to varying degrees, of course - it inevitably leads to disappointment. Marketing is selling you a product, a game's runtime is weighted towards delivering the best early impressions, and stories don't always have a happy ending if a sequel could come instead.
Regardless of whether what we got was better or worse, sometimes even the game's themselves can fail to deliver...