Original jurisdiction does not equate to exclusive jurisdiction.
In addition, Hamilton, in Federalist Paper No. 81 confirms the Obamacare case ought to have been originally filed in supreme Court and not district court which is one of the inferior courts created by Congress:
Hamilton says:
“Let us now examine in what manner the judicial authority is to be distributed between the supreme and the inferior courts of the Union. The Supreme Court is to be invested with original jurisdiction, only "in cases affecting ambassadors, other public ministers, and consuls, and those in which A STATE shall be a party.'' Public ministers of every class are the immediate representatives of their sovereigns. All questions in which they are concerned are so directly connected with the public peace, that, as well for the preservation of this, as out of respect to the sovereignties they represent, it is both expedient and proper that such questions should be submitted in the first instance to the highest judicatory of the nation. Though consuls have not in strictness a diplomatic character, yet as they are the public agents of the nations to which they belong, the same observation is in a great measure applicable to them. In cases in which a State might happen to be a party, it would ill suit its dignity to be turned over to an inferior tribunal.”
And this is why, under “An Act to establish the Judicial Courts of the United States“ Act of 1789, 1 Stat. CH. 20 see: Supreme court, original jurisdiction (scroll to bottom of page) we find:
"SEC. 13. And be it further enacted, That the Supreme Court shall have exclusive jurisdiction of all controversies of a civil nature, where a state is party, except between a state and its citizens; and except also between a state and citizens of other states, or aliens, in which latter case it shall have original but not exclusive jurisdiction."
JWK