Go do a search of the best selling wrestling books of all time, or a list of the NYT bestsellers, and see if you notice a trend.
There is no correlation to book quality, but there is definitely a correlation to star power.
Both of Hogan's books were trash, panned by critics & fans. Both were bestsellers. Chyna's abomination was #2 on the NYT's bestseller list, and it's considered the worst wrestling book of all time.
Now look at books like Lou Thesz Hooker, or William Regal Walking the Golden Mile, the latter of which was pushed hard on WWE tv. Regal couldn't give away copies that book.
Foley (X4), Jericho (X2), Hart, Hogan (X2), Flair, Lawler, Austin, Hardy Boyz, Edge, Michaels, Chyna some of these are good, some are really bad, some average, all big hits. They may not fall in order of who was the biggest star, but the pattern is clear. People buy the books of stars, not the books that tell the best story.
I still don't understand how you are failing to see the bigger point when it comes to Foley's books. "The Rock Says", largely a piece of shit, hit #1 on the NYT beestsellers, im sure that had nothing to do with what a gigantic star he is. C'mon, man.
Also, most if not all of these books don't even exist if Foley doesn't break through with his first.