How can Apple "reign supreme" over the industry, to the point where they're facing significant anti-trust pressure, while also having negligible marketshare? Clearly there is more to this supremacy than raw marketshare.
US marketshare and mindshare among the (US) people who decide such things. If all the relevant politicians and judges and their friends and families (presumably all wealthy) have iPhones...
As well as having 55% US marketshare as other posters have mentioned, they account for 42% of global smartphone profits despite only having 17% marketshare.