You are confusing "banning bitcoin" with "banning bitcoin mining". Nobody can ban bitcoin because it is decentralized and based on peer to peer network that can never be banned. But a mining farm that is extremely hard to move or hide which has a fixed location and relies on a bigger than regular household electrical source is easy to find and shut down.

They want to do the later. And they can easily do that in their own jurisdiction (not globally). For example a couple of years ago one of these Asian countries (I forgot which one) banned mining and then seized hundreds of ASICs. Then they used heavy machines (trucks, etc.) to destroy them in the middle of the street. That action didn't do anything to bitcoin mining as a whole, just in that country.