Epic and Ode.
The great and mighty hero strikes down evil and saves us all. One figure to stand behind, incomparable to normal mortals.
Grotesque Epic and Tragedy
The heroes are no longer strong enough on their own, they have displayed and celebrated weaknesses. They are vulnerable, and thus need to operate in teams. They can be placed into dangerous (for them) situations, and are otherwise no longer perfect. The Superheroes have turned into a Grotesque Epic.
On the flip side, we see a rise in the "Everyman" Tragedy. The great and mighty can fail, but the populace can do great things. We are praising brotherhood and unity with our fellow citizens.
So What Happened?
Mistrust of power (reaction to McCarthyism and HUAC in populace, thus the 'weakness/vulnerability' of the heroes and the rise of the "everyman" hero and the war stories)
Enemy is interior (both the Commies and the Government, thus the 'everyman' since we can trust him and the attacks on the established heroes)
Fear of the loner/different (what does he have to hide?)
Need for solidarity and community (thus the rise of teams and rise of groups of soldiers).