The distribution of winnings is a function of how aggressive you play and how call-happy your opponents are. If you bluff every single hand, your non showdown winnings are going to be good but on showdown you lose at an insane rate. If your opponents don't have a fold button, you don't take a lot of pots without showdown so your showdown winnings are high.
It doesn't really matter how you get the money, as long as you get it. Don't worry about something you don't have full control over and make the right play every hand, regardless of these stats.
