Quantum was popular as "oh god, our cryptography will die, what are we going to do". Now post-quantum cryptography exists and it doesn't seem to be clear what else quantum computers are useful for, other than PR.

Blockchain was popular when the supply of cryptocurrencies was kinda small, now there's too many of them. And also its actually useful applications require having offline power to make decisions. Go on, tell politicians in any country that you want electoral system exposed and blockchain-based to avoid falsifications. LOL. They are not stupid. If you have a safe electoral system, you can do with much more direct democracy. Except blockchain seems a bit of an overkill for it.

3D printing is still kinda cool, except it's just one tool among others. It's widely used to prototype combat drones and their ammunition. The future is here, you just don't see it.

Cloud - well, bandwidths allowed for it and it's good for companies, so they advertised it. Except even in the richest countries Internet connectivity is not a given, and at some point wow-effect is defeated by convenience. It's just less convenient to use cloud stuff, except for things which don't make sense without cloud stuff. Like temporary collaboration on a shared document.

"AI" - they've ran out of stupid things to do with computers, so they are now promising the ultimate stupid thing. They don't want smart things, smart things are smart because they change the world, killing monopolies and oligopolies along the way.