It was part luck no doubt, sometimes feuds just write themselves, it depends if the E can get out of their own way and let shyt happen naturally.
The problem they have is sometimes actually giving the ball to people when they're hot. They gotta get out of the mindset that the only way people can get over is only with their help. Some wrestlers connect with the crowd like Bryan, Cesaro, the Shield, the Wyatts and Punk and the crowd goes apeshyt for them, but in their eyes, they think that the wrestler hasn't earned it yet. That's why ADR and others have bombed, the E thinks they're over with the crowd and that they earned their spot, but in reality, they were given a free spot on the top of the card.
Look at how the crowd turned on Batista, he waltzed in and was given his spot over Punk and Bryan. Punk left, Bryan stayed and they're still the most over in the company while Tista and Orton get booed, or get a random ass chant thrown in their direction, or no reaction, cause the crowd doesn't care bout them. Cena's case is that they're tired of the same shyt, but the 'E ain't gonna alter his character cause he's a money maker to kids and women even though adults and smarks don't like him.