During their visit, he found out that Lindbergh could increase the range of P38 fighters by 700 miles by properly adjusting the engine controls.
MacArthur had him go around to the Army units and teach the pilots how to do it.
That is what started the Island hopping strategy where they didn't need to capture every inland for air strips.
It also made it possible to have enough range to shoot down Yamamoto.
I once thought that, too. However, I checked the dates and found that that is incorrect. Yamamoto was shot down long before Lindbergh went to the South Pacific. At the time Yamamoto was shot down, Lindbergh was in Michigan working for Henry Ford.