Just like people were all cogs in the Hogan, Backlund, and Bruno machines before that. This is how WWE booking has worked since, literally, it began.
Come on.
During the height of Hulkamania, you had 5-7 Saturday Night Main Events, and 3 or 4 PPVs per year.
Did Hogan, Backlund, and Bruno hold the title longer than Cena? Yes (and they are the ONLY individuals to be champion longer than Cena), but they also weren't being exposed to all of their fans across the world on a weekly or semi-weekly basis.
Stone Cold's run at the top lasted from 1997-1999. 1996 and early 1997 built him up (Mania match with Bret, KotR, etc.)
Aside from a 6 month feud with Nexus in the latter half of 2010 and early 2011, John Cena has not gone more than a few months out of the title picture since he first won the damn thing in 2005. And typically when he's not in the title picture, the title takes a backseat to whatever feud john cena is involved in. Sometimes his feud and the title feud intersect, and his part overshadows the title, even! (See: Cena reffing the Barrett vs. Orton title match)
The fact is, John Cena should have undergone a major change around late 2006/early 2007, or at least been moved out of the main event picture. His run at the top should have been 2 or 3 years, from 2004-2006. His feuds with the likes of John Laurenitis and Nexus and Kane never should have been the focus of RAWs and PPVs, they should have been secondary to any title feuds going on (The exceptions are when you have survivor series-type matches against the Nexus or the head of Nexus becomes involved in the WWE title picture.... but John cena NEVER should be the main focus, just a factor in play!)
Everything John Cena does is treated as the most important thing in the company, booking wise. It's been that way for nearly a decade, and it should have changed about 7 years ago.