Why did Robert leave Kristen?

Kristen Stewart, Robert Pattinson & Taylor Lautner Immortalized With Hand And Footprint Ceremony At Grauman's Chinese TheatreGiven their stardom, it took hours for their separation to become a topic of public knowledge and for every celebrity news site to report that the couple had split up at the end of last week. Yesterday, he was seen driving away from her home in L.A. in his own pickup truck (sporting a kick-ass beard!), filled with his belongings and accompanied by his dogs, Bear and Ernie, so it may be safe to say this time it may be final.

Speculation has been flying since then about what prompted this new separation and the winning theory so far given statements from their friends seems to be that Robert simply had enough of Stewart’s sour moods and who wouldn’t be? We’re trying hard to figure out over here what reasons a millionaire young actress with millions of fans could have to be constantly ill-tempered and we’re coming up short! The catalyst seems to have been when the actor blew off a party Stewart arranged for him on his birthday, the 13th of May and but of course, one can’t forget the fact that she cheated on him a while ago with film director Rupert Sanders. That must’ve been one hell of a happy household.

Fans are also concocting crazy theories about how singer Katy Perry might’ve purposely split the couple to steal Robert away, since they’ve been spotted together at a number of occasions over the past year, but she’s reportedly a friend of both him and Kristen, so that might just be the denial kicking in. Still, who could blame him if this were the case?

What are your theories about the split up?