Even if we can't agree on the exact number, we can say for certain RadOnc is tiny compared to the rest of Medicine.
Rounding way, WAY up on the highest estimate, there can't be more than 6,000 American RadOncs (my current, personal estimate - more data driven than the Workforce Taskforce - is 5,300).
My current best guess for the "academic RadOncs at programs with residents" is ~1,200 (based on 2016-era work from Emma Holiday).
The majority of the echo chamber publishing we see in the ASTRO-associated journals comes from those 1,200. Just like any specialty, there's a smaller subset of those folks who have a significantly higher output in terms of volume/velocity.
But...Los Angeles High School alone has around 2,000 kids. There are more high school students at that one school in that one city than there are all academic faculty at residency-associated departments in all of America.
Put another way:
Being a "RadOnc KOL" is like being a popular high school kid. Sure, a certain group of people will "know who you are" and you build an entire identity around that.
...however, it's healthy to remember (for all of us) that most people have no idea who we are.
I find it freeing!