I served as the secretary for the Coast Guard naming board. The naming board is for both vessels and full, permanent buildings (annexes, temp. buildings, outdoor structures like streets, BBQ pits etc are at command discretion).
Each class of ship has guidelines for naming. I can speak specifically to the members of the naming board for a Navy ship, but in general the Coast Guard naming board is made up of people like the Coast Guard Chief of Public Affairs, Coast Guard Historian, the Master Chief Petty Officer of the Coast Guard....and a number of others, mostly flag officers.
Politics plays into decisions. "Do we have enough blacks, hispanics, or females represented" in naming ships? Each service feels the pressure of showing how diverse it is.
In the case of the Coast Guard, I would maintain that more deserving white males were overlooked to name a cutter after a couple of female lighthouse keepers. Longevity doesn't make someone "historically significant". We just did it with our first 13 cutters of a new class. Based on the naming scheme, I don't see how they aren't going to have to water it down even more.
What would have been easier, and in my opinion, "cooler", give them the old British names, kind of like the "Reliance class" cutters. The "Sentinal Class" started like that until it received resistance within the Coast Guard. Wonder why.
What did Chavez do for the Navy specifically? Was he the "hispanic" check in the box? Was Earhart the "female" check in the box?