After watching this movie...
I'm not surprised that Brad and Angelina got together. Damn they were physical with each other. Even though we see no explicit nudity, there is a lot of physical interaction that's demanded of them. Angelina pressing her bare boobs against Brad, Brad groping her breast when he's searching her, both of them grabbing and slamming each other VERY HARD.
And that's even without the "explicit sex scene" that was cut out? ..well actually I may be counting that already, I'm not sure if I saw the version with it or without.
Not excusing what they did (I'm assuming they did stuff before Brad broke up), but damn they basically had foreplay with each other, not surprised something happened out of it.