Visual Capitalist is clear about its methodology for calculating each state's "biggest" public corporation. It's basing size on market capitalization.
It would, however, become a different map if size in terms of number of employees, or "total salaried payroll" or the size in terms of revenue dollars as a base for tax payments to the state as the data benchmark, to look at the impact those companies are having on the states' individual economies.
As one commenter to the post notes:
Chipotle in Colorado is nothing compared to say Excel energy, Coors, or Lockheed Martin. (For employment – Colorado has many Govt employees too.)
Yes, in some states, the biggest public company is the government.