When DC Comics acquired the properties of Charlton and later MLJ aka Mighty/Archie Comics, at first they tucked them away into their own fictional universes and repackaged them in the forms of the Watchmen and !mpact Comic, which we've previously considered.
However, there was another attempt at actually integrating the core characters into the mainstream universe at DC Comics, for the first time exposing these comic creations to a massive audience.
As with every comic book line, there are certain archetypes or niches that have to be filled to justify their existence to the public-at-large. Such was the case here.
Captain Atom was reintroduced to a new generation initially during the Crisis on Infinite Earths along with several of his Charlton Contemporaries. However, once his compartmentalized universe of Earth-Four was integrated into the main DC universe, he was reimagined in a way some considered dramatic and others considered overkill.