He was a 5th rounder, who was projected to go in the 2nd, and was always viewed as a high potential guy. A lot of teams were worried about Mookie's size and a lot of people thought he wouldn't sign because he was a Tennessee Kid and had a scholarship to play there, IIRC Sox had to overpay the slot in which they drafted Mookie by a lot. I could definitely see someone being early on Mookie bandwagon and falling in love with his play style. I remember the first time I saw him play in the minors, I instantly had a man crush on the guy. He's literally one of the few players I don't see how anyone could hate. I have Yankee fan friends who even love Mookie, they hate playing against him, but they cant actually hate him as a person. I Love the way he plays the game, and especially love his work ethic. He is a very special player.
Edit: Here is actually a very good article I found about Mookie regarding why he and Mike Trout fell in their respective drafts, and are now arguably the two best players in baseball
https://www.masslive.com/redsox/index.ssf/2017/02/how_mike_trout_mookie_betts_we.html