The existence of a quantum computer is real dude, but people don't understand that. Basically, they must understand how a quantum computer works.
The problem is SHA 256 is not safe anymore consider it doesn't give a lot of protection as it will be so easy to be hashed and there should be a quantum resistance.
It's not the end for the world but crypto goes wild if the quantum computer will be used for crypto.
that's not true if a quantum computer is still a prototype only. Did you know about d-wave?
https://www.bloomberg.com/news/articles/2018-06-29/why-quantum-computers-will-be-super-awesome-someday-quicktake
Some big companies like google and IBM are still developing their own Qcomputer
https://www.wired.com/story/googles-quantum-supremacy-isnt-end-encryption/
https://www.ibm.com/quantum-computing/learn/what-is-quantum-computing/