Does Bitcoin Have a Mining Monopoly Problem?

During bitcoin's early days, anyone could "mine" it using their home computer. But as the price of digital currency climbed towards $100 in 2013 (it's now over $4,000), professional mining groups with specialized computer chips emerged. Today, these groups, or pools—nearly all based in China—have become concentrated and now dominate the production of new bitcoins.
This phenomenon is not new, but an article in Quartz this week shows how pervasive it is. The article looks at a company called Bitmain, which became a powerhouse by developing ASIC chips used just for bitcoin mining:
Bitmain may now be the most influential company in the bitcoin economy by virtue of the sheer amount of processing power, or hash rate, that it controls. Its mining pools, Antpool and BTC.com, account for 28.9% of all the processing power on the global bitcoin network.
The piece, which describes Bitmain's plans to move into artificial intelligence, profiles the company's co-founder Jihan Wu, a controversial figure in the bitcoin world—in part over allegations he manipulates the crypto-currency for his own ends. This includes the recent schism that saw bitcoin's blockchain (the record of all transactions) split in two, creating a new currency called "Bitcoin Cash."
Critics of Bitmain suspect that Wu was behind the recent, somewhat related split of bitcoin called the bitcoin-cash hard fork. That split was supported by a miner in Shenzhen named ViaBTC—which happened to be a company that Bitmain has invested in.
If the allegation is true (for the record, Wu denies them), it suggests bitcoin is vulnerable to market manipulation not just by traders who hold large stores of bitcoin, but also by miners like Bitmain.