There was but it wasn’t well known. There was a photo of him earlier this year, showing massive weight loss. And then a bunch of not reputable online articles about him being taken to the hospital in a wheelchair but covered up because of covid. I looked all over the regular news sources for confirmation it never got it, so thought it was fake. It’s morbid and in a way beautiful. Obviously not that he passed this early but that we really did have no idea and yet still he kept fighting, not letting his battle dim his spirits or those of the many people who looked up to him. As you said, incredible effort, energy, etc. and all of that made him immortal in the minds of millions. Leaving that kind of legacy is about the best anyone can do.
If it was kept a secret which it sounds like it was, good for him. He didn’t spend those 4 years fielding question after question. Like, cancer may take your life, but the attention to it from the prying eyes of the world takes the life out of the remaining life. It can be full of encouragement, but it’s such a focus that being able to live the best you can while the doctors fight it for you, becomes a tragedy in itself. The man is a Legend, and he will be missed so much.