Here's why:
* John Wayne and Maureen O'Hara starred in several films together, many of which were set in Ireland or had Irish themes. Some notable examples include "The Quiet Man" (1952), "The Wings of Eagles" (1957), and "McLintock!" (1963). However, none of these films won two Oscars.
* "The Quiet Man" is arguably their most famous collaboration and is considered a classic of Irish cinema. It won two Academy Awards, but they were for Best Cinematography (Color) and Best Sound Recording (Sound Recording), not for Best Picture or any acting awards.
It's possible you're mixing up some details, but there's no record of a John Wayne/Maureen O'Hara film about Ireland winning two Oscars.