How, and why, is Robert Downey Jr. returning to Marvel? The actor is finally speaking out about the shock announcement.

On Tuesday's episode of The Hollywood Reporter's "Awards Chatter" podcast, Downey shared the story behind him agreeing to return to the Marvel Cinematic Universe as Doctor Doom in the upcoming film "Avengers: Doomsday."

The "Iron Man" star, 59, explained that after leaving the Marvel franchise, he stayed in touch with Marvel Studios President Kevin Feige and planned to go to Disney CEO Bob Iger with an idea about how he could "be of service" to the company's theme parks.

But during a meeting Downey and his wife Susan subsequently had with Feige, the Marvel boss floated the idea of bringing Downey back on screen — despite the fact that his character, Iron Man, died in the dramatic conclusion of 2019's "Avengers: Endgame."

"He said, 'It just keeps occurring to me that if you were to come back ...'" Downey recalled. "And Susan was like, 'Wait, wait, come back as what?' We both realized over time that it was another thing that just disproves any doubt anyone could ever have about that guy, a very sophisticated creative thinker."

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According to Downey, Feige brought up the idea that he could return as Victor Von Doom, the iconic Fantastic Four villain who is traditionally an adversary of Reed Richards. "I looked into this character, and I was like, 'Wow,'" Downey said. "Later on, he goes, 'Let's get Victor Von Doom right. Let's get that right.'"

The "Oppenheimer" star described this as an effort to "not go backwards" and "continue to beat expectations."

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After the meeting with Feige, Downey went to Iger's house to discuss the idea, and the Disney CEO gave it the thumbs up. "He goes, 'I like it,'" the actor said.

Marvel announced Downey's return at the end of a Comic-Con panel last month, with the actor walking onto the stage wearing a Doctor Doom mask and dramatically taking it off to reveal himself. Director Joe Russo said that Downey's return is "proof of the unimaginable possibilities in the Marvel multi-universe" and called the actor "the one person who could play Victor Von Doom."

But fans were confused given it was not clear whether there will be any connection between Doctor Doom and Downey's previous Marvel character, Iron Man. Some theorized that Doctor Doom will be depicted as an evil version of Tony Stark from an alternate universe. Others argued that Doctor Doom will simply happen to look like Tony Stark, but there will otherwise be no connection between the two, similar to the way actors like Gemma Chan have played more than one unrelated Marvel character.

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While Downey did not confirm which theory is correct on the "Awards Chatter" podcast, his statement about Feige wanting to get Victor Von Doom "right" could suggest he will be playing a comic-accurate version of the character, rather than an evil Tony Stark variant. The Iron Man variant concept was controversial among fans, some of whom were disappointed in the idea that Marvel might not be faithful to the character's comics history.

Downey's return represented a pivot for Marvel, which originally planned for Jonathan Majors' Kang the Conqueror to be the villain of its next "Avengers" film, previously titled "Avengers: The Kang Dynasty." For Downey, it will be a homecoming after he won an Oscar for best supporting actor for his role in "Oppenheimer" earlier this year.

While it was widely assumed that Downey would eventually return to the MCU, most fans thought he would be back as an alternate universe version of Tony Stark, not a new, villainous character.

Gwyneth Paltrow, who played Tony Stark's love interest Pepper Potts in the "Iron Man" and "Avengers" films, previously joined in on the confusion about his return. The actress commented on her former co-star's Instagram last month, "I don't get it, are you a baddie now?"