EXCLUSIVE

Bruce Jenner is a simple man who likes simple things, and Kris is the exact opposite, which is why, according to a very connected family source, Bruce finally said, "F**k this s**t" and he moved to Malibu.

Several family sources all confirm ... Bruce has always been "a simple man" who likes 3 things -- golf, racing cars and RC helicopters. He has always shunned the "Hollywood life" and it makes him extremely uncomfortable.

Kris -- in case you didn't know -- is ambitious ... some say to a fault. One family source put it this way: "She's on a freight train and Bruce finally wanted off."

We're told Kris wasn't the one who wanted Bruce to move out, because it wasn't good for the show or the Kardashian brand. It was Bruce who just got sick of it. It wasn't that he was bossed around or got into big fights with Kris -- it's just that he wasn't happy around her.