Re: "what’s most surprising is that it is 60-year-olds that were investing the largest amounts into it with an average total of 6.58 million won ($6,119 USD)." Well, that may hold in the US also as I am in my late 60's and have invested about that amount. And so have a few friends my generation.
Re: "Bitmain : Bitmain is the largest player in the ASIC miner business and holds 70 to 80 percent of the market."
Don't you think that holding such a large share of the mining undermines the decentralization concept of Bitcoin and all other cryptos?