I know that superhero comics weren't selling so well, so they got rid of a lot. Obviously, Superman and Batman were strong titles then.

But have we ever heard anything about why Green Arrow and Aquaman continued v. any other heroes? I can see that Flash and Green Lantern had since had their titles canceled, but had they actually become less popular than those two? And was there ever any indication on whether Wonder Woman's sales merited keeping her own title or if it was only done for legal reasons, to keep IP (seems unlikely, since Sensation Comics wasn't canceled in 1949 like GL and Flash - her struggles may have come a bit later and that's another discussion worth having, but would need old sales history).

Which was the first of the previously-popular heroes to be removed from publication in the era?