By any measure, Captain America is one of the greatest superheroes in the Marvel Universe. He was the first Avenger before the superhero team was even a thing and he has led the charge in some of the biggest battles in the history of Earth's Mightiest Heroes. Steve Rogers and his red, white, and blue shield are a symbol of hope and inspiration to everyone in the Marvel Universe. He inspires others -- whether they are regular people or superheroes themselves -- to be better, stronger, and more compassionate. It's been that way for years.
Despite years of trust, the people's faith in the Sentinel of Liberty was eventually broken. For the past few years, Steve has been working hard to clear his name, and to earn back the people's trust. But why was it broken in the first place? Well, this struggle is actually the consequence of a series of events that started five years ago, when the character was revealed to be a secret agent for Hydra.
Old Man Steve Rogers
The road to Steve Rogers becoming the Hydra Supreme began a long time ago, in 2014's Captain America #21 by Rick Remender and Nic Klein. In the issue, Steve engaged a villain known as the Iron Nail in combat. However, the villain ended up removing the super-soldier serum from Steve's system. As a result, Steve lost his powers and his body aged to that of a 90-year-old man -- his rightful age.
However, he didn't let that stop him. While Steve stopped being Captain America after losing his super-soldier status, he still remained active as the head of S.H.I.E.L.D. for a few years. That eventually came to an end in the 2016 Avengers: Standoff! event.
How Kobik Turned Captain America Into a Hydra Agent
In the Avengers: Standoff! storyline, it was revealed that Maria Hill and S.H.I.E.L.D. had created a town called Pleasant Hill. The small town's inhabitants were actually all supervillains whose lives, identities and memories had been erased and altered by the sentient shard of a Cosmic Cube called Kobik. Taking on the appearance of a little girl, Kobik was used to create this perfect illusion, but hell eventually broke loose when the villains regained their memories and their identities.
A big battle took place involving the Avengers and the then-current Captain America, Sam Wilson, as well as Bucky Barnes and Steve Rogers. However, in the fight, old man Steve Rogers was severely beaten by Crossbones. Before the villain could finish him off, Kobik used her powers to restore Steve as a super-soldier. Suddenly, Steve was young again and fully powered as Captain America.
While it wasn't revealed at the time, Kobik hadn't brought back the actual Steve Rogers. Instead, she had created another, alternate version of him.
Captain America in Secret Empire
Later, readers learned the Red Skull had actually manipulated Kobik into believing Hydra was a force for good. Therefore, when she brought Steve Rogers back to his youthful self, she made changes to his timeline. Steve was still the world's greatest superhero, but he was actually a secret agent for Hydra and kept his true allegiances under wraps until he was finally ready to make his move in 2016's Captain America series.
The evil Steve Rogers worked in secret to launch a full-scale attack to make Hydra finally rule supreme all over the country. In the 2017 event series Secret Empire, he locked out the cosmic superheroes from the world thanks to a planetary shield, plunged most of New York in a dark bubble reality and destroyed Las Vegas in an attempt to kill the Avengers.
Thankfully, the conclusion of Secret Empire revealed this evil Steve Rogers was actually a double. A part of the real Steve Rogers was in fact still alive inside the Cosmic Cube. There, he had no clear memory of who he was. Eventually, inside this reality, Steve found Kobik, who gave him back all of his memories. While he was still trapped, however, the Winter Soldier went inside the Cube, and he was able to bring both Kobik and Steve Rogers back into the real world.
Now, there were two Captain Americas: one evil, who swore his allegiance to Hydra, and the real Steve Rogers, who had finally properly returned. Both versions of the Sentinel of Liberty fought one another for the fate of the world. The real Steve defeated his evil counterpart, and he stood victorious against Hydra. As the event came to a close, Captain America had finally returned, and the evil "Captain Hydra" was locked up. However, the damage was done, and the public now associated Steve Rogers with the man who had nearly destroyed the country.
After this, Steve went on a cross-country tour of America to try and restore the public's trust in the red, white and blue shield, but his trip was cut short. In the subsequent Captain America series, the villainous group known as the Power Elite used that broken trust to their advantage, but Steve and his allies fought to remind everyone who Captain America really is -- and what he stands for.