Here's a revealing article from THE JACK KIRBY COLLECTOR issue 60 (Jan 2013), titled "Key 1960's Moments", a 4-page chronological timeline of events at Marvel leading to Kirby's departure, going year by year from 1961 to 1972.
https://readcomiconline.to/Comic/The-Jack-Kirby-Collector/Issue-60?id=110616#68

It cites Stan Lee's denied story credit and payment for stories reprinted in FANTASY MASTERPIECES by Kirby, Joe Simon, Carl Burgos (creator of golden age Human Torch), Wally Wood (denied plotting and creative credit on his then-current DAREDEVIL run), Steve Ditko (similarly denied story and creative credit on SPIDER-MAN and DOCTOR STRANGE), and Bill Everett (denied story credit and compensation on reprints of golden age Sub-Mariner stories).

So it wasn't just Kirby or Ditko who were denied credit, denied compensation or denied creative control of the characters they created for Marvel. They were even shorted credit and payment for licensing, comic book reprints for licensing, and Merry Marvel Marching society profits and t-shirts! The 80,000 Marvel t-shirts alone sold on Stan Lee's college lecture circuit, if you estimate the t-shirts sold for $5.00 each, that's $400,000 in gross profits. And then shorted from that, Kirby had to borrow $2,000 from Martin Goodman for his moving costs to California, that took him years to pay back!

Also interesting how Stan Lee went from staeling the glory from Wood for his contributions on DAREDEVIl, compelling Wood to resign in disgust, and Stan Lee just went on to swiping ideas and shortchanging credit from the next artist to draw the series, no lesson learned or better treatment of co-creators going forward.

I didn't know till now that Captain Marvel and the Kree was begun in MARVEL SUPER-HEROES 12, or that Kirby (again uncredited) created the concept.
The timeline through 1970-1971 explains a lot about how Kirby''s stories in AMAZING ADVENTURES 1-4, SILVER SURFER 18, ASTONISHING TALES 1-2, and CHAMBER OF DARKNESS 3-4 came to be created. And toward the end, a lot of editorial changes and creative harassment by Stan Lee, showing his bad treattment and perhaps deliberate harassment of Kirby at the end. I was blown away that Kirby did a Silver Surfer story in FF 74-77, and then right after SILVER SURFER 1 by Lee and Buscema came out the next month, and Kirby was kept completely in the dark about the Buscema series until right before it came out! His own creation. "Kirby felt he had lost creative control of his own character." Yeah, you think?!?

Again, everything Kirby was cheated out of, is now given without reservation in the standard contract for Marvel writers and artists. And if given back then, Kirby would likely have spent the rest of his career at Marvel.