That's a negative on that question. The miners cannot decide anything by themselves, even if they all worked together. In Bitcoin we have five constituents, of which none has full control over the system: Developers, Miners, Nodes & Wallets, Users and Retailers. They all have their own interests which partially even contradict the interests of others. That's why it is called a 'consensus network'.

Even nation states wouldn't be able to take over or take down Bitcoin anymore, because the network has grown too strong by now. Here's a link to a video I transcribed, where Andreas Antonopoulos explains why Bitcoin is so resilient against attackers: