This confirms that mining is very centralised and controlled by a few institutional investors acting in their own interests and not those of the other participants. Is there a chance to know who are the investors of Foundry, AntPool, F2Pool and ViaBTC?
In theory everyone can join the network, but in practice those who actually participate in the PoW consensus (51%) and produce blocks are less than 0.1% of the miners, i.e. those 50-60 miners reported in the research. To achieve such a high hash rate, it is necessary to have a mining farm and an economy of scale.