How is cornering the market outright illegal? And in which jurisdiction?
There are plenty of examples where one company has a strongly dominant share. Diamonds are an obvious example, search engines are another.
Commodity trading in the major markets (US, EU) has rules against cornering and other forms of obvious market manipulation. Obviously that only applies to "commodities", whereas it's accepted that manufactured goods have a limited number of suppliers regulated by patent. The entire market for pharmaceuticals is "cornered" in that sense.
Yeah, i mean, it's not like silly things related to market manipulation in commodities happened for many years before anything was done about it: