[Cozumeleno]

I may be mistaken but isn't an induction for a player based almost entirely on statistics?

Not really. Stats probably have the biggest bearing for many voters but there are plenty of other factors at play here. The Hall of Fame's official criteria, in part, is as follows:

Voting shall be based upon the player's record, playing ability, integrity, sportsmanship, character, and contributions to the team(s) on which the player played.

How those are weighted varies among voters, but the one thing that is clear is that a lot of other things go into voting outside of stats. That whole part about integrity and, in some cases character, is that pesky issue keeping stats-heavy steroids guys out, for example. In Jackie's case, he didn't only make a big contribution to his team, but the entire league. Those last four criteria are really key in his case (and, not to mention, he was a pretty good player).

We can argue how much stats should be a part of that, but again, it goes much deeper.