Well. Comics aren't really subject to conventional narrative or marketing rules for a variety of reasons. Crazy stuff like this is often necessary to keep the characters in the public view, even within the confines of publishing. When Captain America, Spider-Man, Iron Man, Superman, the X-Men, the Fantastic Four and Batman were created, their creators had no idea that they were starting a decade-spanning, serially ongoing, continuity based narrative with a floating timeline and a shared universe.
Eventually, the creators had to choose what they could change and what had to stay the same as they couldn't keep writing 60s era stories when in the 70s and 80s. Sometimes, the choices were effective. Sometimes they were a mistake. Sometimes, creators and companies stuck to their guns and carried forward, other times, they decided to use the flexibility of the medium to roll things backwards.
Spider-Man, for example, graduated from high school and went to university. With the X-Men, sales were low and Marvel cancelled the book, later reviving it with a largely overhauled cast that proved to be more popular than the first generation. Things changed for both Spidey and the X-Men: Peter Parker married Mary Jane and she got pregnant. With the X-Men, Jean Grey died, Magneto became a hero, Cyclops got married and retired, Professor Xavier left the X-Men in the hands of Magneto while he went off to space. Barry Allen died and Wally West replaced him. The feeling was that these characters would only ever exist in comic books, so comics were free to evolve and change and rework constantly, often making what would theoretically be irreversible changes.
In the 90s, however, Marvel started selling their TV and movie rights and suddenly, there became an urgent need to start rolling back all the changes; to make the comics reflect the default version that a TV show, cartoon or film would use. For the X-Men, all the changes were undone. Magneto reverted to villainy, Jean Grey was resurrected, Cyclops' wife was revealed to be some sort of demon queen and the clock rewound. The fact that previous comics had shown the X-Men to have outgrown this 'classic' situation was discounted.
With Spider-Man, Marvel attempted to retire Peter Parker and bring in a new Spider-Man, a clone named Ben Reilly. The sales crash made it clear that fans' loyalty was not to the costume and the name, but to the specific character, and Peter was reinstated with a time travel plot later undoing his marriage to Mary Jane.
With Wally West, DC saw which way the wind was blowing and decided to make their FLASH comics reflect any future TV show rather than see a TV show force their hand. When Wally became the Flash, the creators had no way of knowing that TV adaptations would be made, that superheroes could become filmable, that their third gen Flash would have a story too complicated to render onscreen.
All this experimentation, some incompetent and some brilliant, eventually made it clear: the comics would inevitably revert to the default status quo that a TV show or film would use. But in the 2000s, Marvel and DC began experimenting with making the kinds of massive changes they'd always had to roll back -- except this time, they would plan out in advance how the rollback would take place and make the experience a strong journey with some lasting effects here.
For example, Captain America was killed off and there was a multi-year story where we saw how the Marvel Universe coped without Steve Rogers and Bucky had to step up and grow a lot. Meanwhile, Norman Osborn took over the Marvel Universe. Eventually, Steve returned, toppled Osborn, but Bucky remained Captain America until his Winter Soldier past was exposed and he stepped down. Things went back to how they started, but the circle was a fun ride.