When otherwise smart people do seemingly dumb things, you have to ask if there is some rational explanation for the behavior. My take, having experienced everything you describe here, is that from upper management's position, each of these new shiny objects is a bet. Maybe it'll work out (networking, internet, cloud) or it'll go bust (push, blockchain, etc).

If it works out, the company gets to ride a new tech wave while avoiding obsolescence (see Yahoo, DEC, Sun, etc). If it doesn't pan out, the company writes off the investment and moves on to the next shiny thing.

From the leadership perspective, it actually makes sense to jump on the latest shiny thing. From the mid-level manager's perspective, it sucks to be the one who has to go make sense of it.

I spent time at Google and found this to be the case as well. I think the only "cure" for this is good upper management that is isn't swayed by the flavor of the moment hype, and also a culture of being monomaniacally product-focused.

Places that are intensely product-focused aren't immune from frothy hype, but at least it's forced through the critical filter of "ok but what does this do for our product really", which is a vital part of separating the wheat from the chaff when it comes to new ideas.

My main beef with Google is that the company's culture is intensely not product-focused. The company's defined by its origin story of a groundbreaking technology that happened upon product-market fit, and it's pathologically unable to do the opposite: start with a clear-eyed product vision and working backwards to the constituent technologies.

Maybe a minor tangent, but I really enjoyed playing with Google Assistant when it first came out. Great novelty, especially asking it for jokes.