One of the things that may have caused Earhart to underestimate the risk was the high reliability of AM medium wave radio broadcasting in the US over long distances, with over a dozen 50,000 watts and higher clear-channel stations, each serving about half the country reliably just about every night. But short waves (around 7 MHz) in the tropics during daylight with a 50-watt transmitter, and a receiving antenna that you lost on takeoff, is a far different situation. For the trip from Hawaii to the US, their plan was to home in on a powerful AM broadcasting station in Los Angeles, which would rewire its antenna to send most of its power to the west. That might have worked, depending on the time of day.
Not to mention "just fly east" will get you to land just fine from Hawaii. It might not be the land you were looking for, but it will be land - so even if the direction finding failed the error would be survivable.
They didn't, and still don't, teach radio theory for a pilot's license. Can you calculate the ideal quarter-wave length of a single-line antenna for a given frequency?