Minor vs Happersett
In 1875, Chief Justice Morisson Waite wrote the opinion of the court on a unanimous decision, containing the following definition:
...the court observed that new citizens may be born or they may be created by naturalization and that the Constitution does not, in words, say who shall be natural-born citizens. Under the common law, according to the court, it was never doubted that all children born in a country of parents who were its citizens became themselves, upon their birth, citizens also. These were natives, or natural-born citizens, as distinguished from aliens or foreigners.
The biggest failing of all was allowing a person to become a nominee for Potus without an absolutely rock-solid determination of birth status. It could not have reeked any more strongly of fabrication and cover-up yet because he fit the narrative, no rigorous vetting occurred and even if an ex post facto law were passed, it is impossible to undo what was done.