This is a timeless truth in wrestling. There can't just be one dominant entity. John Cena's domination of the main event over the last few years has taught us that such booking will get stale. By 2010, we got to the point where there were no believable opponents left for Cena.
It's indicative that this is the direction WWE Creative is going with Randy Orton on SmackDown. With his feud with Christian seemingly over, he can now ask why Christian wasn't preserved as a main event talent on SmackDown, as opposed to looking like Orton's inferior.
It's well established that Mark Henry is not very exciting in the ring. He clearly can't move very fast, and requires strong opponents to look good. Randy Orton is a great opponent.
Orton has a huge fan base right now. While personally I don't like him, you can't deny the mainstream WWE audience loves him. With his incredible popularity, the most logical booking is to pair him up against a dominant and dangerous opponent. An opponent who will allow Orton to elicit sympathy from the crowd.
Perhaps this was the downfall of Christian. Orton is consistently booked as near-unbeatable. With Christian booked as the weak heel challenger, who can be blamed for not buying in to him?
However, the WWE has yet another chance to create a real challenge for Orton. Mark Henry's stingiest suit is his monolithic presence, and ability to portray a monster heel. It compliments his slow in ring style, and he has proved that his mic skills as a heel are far greater than his abilities as a face.
Without a doubt, Mark Henry is already looking like a dominant force on SmackDown. Logic states that he should win the World Heavyweight Championship through the destruction of Orton. Randy would gain sympathy from his fan base, and could be far more effective if he is chasing the World Heavyweight Championship.