I am afraid that I cannot start to analyse what happened in comics for girls but I do know what happened in comics such as The Victor, The Eagle and The Hornet.
Although derided by English teachers because they were not actually books, these were of great social value.
They promoted: courage; fortitude; decency; kindness; honesty. Their heroes did not have 'feet of clay' and ambivalent philosophies.
They wanted to see achievement in all areas and did not give us manufactured icons for silly hero worship but rather fictional creations who embodied moral completeness - ones whom children might wished to emulate - and often did.
Their loss has been serious and their replacement by the likes of Grand Theft Auto and other such monstrosities has done us few favours as a nation.