Mazeroski is an interesting one, because both the eyeball test from the people who saw him and all of the metrics say that he was the greatest defensive 2B of all time. Throw in the iconic HR, and does that warrant a spot?
We also have to remember, that while we all pick on these middle infielders, historically pre 1970 or so they were asked to play the game differently than we ask them to play it now. They were defense first positions where any offense you got was viewed as a bonus. MOst were asked to bunt, slap the ball the other way, and not strike out. So while guys like Reese & Rizzuto look mediocre offensively with 2013 eyes, guys like that who brought something to the table offensively were very valuable. That's why Reese accumulated 60 WAR with those numbers, and Rizzuto was winning MVP's.
So by the standards of their competition, you can sorta see why their contemporaries view them as HOF'ers.