A major Japanese Bitcoin mining pool just pulled the plug on its Bitcoin service just as 3 mega-miners claimed 60% of the network

By the time SBI Crypto pulled the plug on its Bitcoin pool in Japan on July 31, its seven-day average hashrate had fallen 64% in a month. Later that day, a Hashrate Index reading put Foundry USA, AntPool and F2Pool at 60% of recent blocks. The timing makes them look connected. Weekly data tell a messier story.SBI Crypto's official update set the first cutoff at 22:00 UTC on July 30, or 07:00 JST on July 31. Share acceptance stopped, and miners began a graceful disconnect. The company scheduled a full Stratum shutdown by 23:59:59 UTC. Its website would stay open for historical data and payout status. The final payout schedule remained unspecified, as did the end dates for API and portal access.At about 11:22 UTC on July 31, Foundry held 26.67% of attributed blocks, AntPool 17.13% and F2Pool 16.21%. SBI Crypto was down to 0.72%, or an estimated 6.8 exahashes per second. The dashboard moved again within minutes. The 60.01% reading captures a moment, rather than a lasting level of control.SBI Crypto's daily telemetry charted a month-long retreat. Its seven-day average BTC hashrate dropped from 16.222 EH/s for the period ending June 30 to 5.817 EH/s for the period ending July 30. By 11:...