WWE just authored the biggest thank you note to WWE fans possible to cap off Sunday night's stellar Money in the Bank pay-per-view. 

It didn't just run over while letting a classic story unfold in the main event between Roman Reigns and Edge. It didn't just organically write Seth Rollins into the feud, laying the groundwork for a must-see SummerSlam. 

It even brought back John Cena for the big one—and the live crowd went nuclear. 

Truth be told, much of Sunday night was fan service as something of a salute to a packed stadium after so long doing shows in front of quiet arenas. Bobby Lashley looked like a monster to set up a big SummerSlam feud. Charlotte Flair got a title back for an inevitable Becky Lynch return. Big E got his big moment, winning a briefcase that lets him cash in whenever, wherever. 

But that main event was a whole different animal. 

While it wasn't the most amazing in-ring match (there were a ton of rest holds and an expected broken-barrier spot outside), it told a good story. It even dotted all of its i's by having The Usos attempt to briefly interfere to save Reigns, only to get rebuked by the Mysterios. Rollins' multiple interferences was just good writing too, even if WWE beat fans over the head with it, telegraphing it a bit with that pre-match interviewer backstage. 

The whole thing sets the stage for what could be a historic SummerSlam on August 21, and we know all of two matches coming out of Sunday night. Rollins had a justifiable beef with Edge, who cut the line for a title shot. Now he's the heel going into a match that has been fantasy-booked by fans for more than a decade.

As a bonus, by way of the interference Sunday night, we also have the groundwork for another Rollins-Reigns feud. 

And realistically, this upcoming Cena-Reigns angle is the story WWE always wanted to tell—with this sort of fan reaction. 

Well, WWE has that reaction now and struck at the perfect time. Cena, in many ways, is still the same old guy, just with a splash of the old "absence makes the heart grow fonder" in there. It's Reigns who avoided that fate, doing the now-historic heel turn and going on a run that, even though it's nearly a year old, still manages to feel amazingly fresh almost every night out. 

So yes, a Reigns-Cena confrontation isn't exactly new, but the vibe of this one is. Reigns is the big bad boss type almost in a Lesnar-ish sense and has just been insulted by a returning legend who used to occupy a role he shook free of to amazing results. 

And to say this feud got off on the right foot is about the understatement of the century. WWE could have waited for SmackDown to roll out Cena. Instead, with the live crowd thinking they were getting a throwaway line from Reigns before the PPV faded to black, they brought out the veteran anyway. 

Cena didn't throw a punch or even threaten anyone. But when that music hit, fans just knew what time it was. He got in the ring, said you can't see me to the guy asking for acknowledgment and that was it. 

Really, that's all the feud would need. The two could not say another word to each other until SummerSlam and the match would feel like the biggest prizefight of the year. But the sheer layers to the relationship between Cena and Reigns on micro and macro levels, even real and fake, guarantee some of the most fire promos fans will see this decade. Try not to forget Paul Heyman, mic-skills legend, happens to be involved, too. 

We're maybe thinking a little too far ahead with the spitballing here, too. But if Reigns gets through Cena, this still leaves the door ajar for some stunning WrestleMania hypotheticals in time. Think, a returning Brock Lesnar with Heyman stuck in the middle, or maybe even pulling The Rock out of a soft retirement to settle a family matter. 

It's only fitting it was Cena this time, though. He's the right guy at the right time. Even his loudest detractors would probably admit that even at their lowest hype levels for him, their beef was with the stagnant nature of the character and move set—they still appreciated him more than almost anyone else (Reigns, after returns from health-related battles, can surely relate to that feeling). 

As it stands, it's Cena who swoops back in to a dramatically changed WWE, a change headlined by Reigns himself, right as the pandemic era fades and we get into whatever this new stretch will earn as a moniker. Alongside the man he passed the torch to, it's Cena who will welcome fans home to the friendly confines of the sport they love. 

All those years ago, WWE captured lightning in a bottle with Cena's rise. Let's say it knew where the bottle that contained Reigns' heel turn was, it was a matter of wanting to pop the lid off. Now it's got another possible moment like that with this feud right as fans get back in the stands after time away. 

That it's this feud at this time is a pretty encouraging thing for WWE as it slams the pedal to the floor. Matchups like this, between guys who carried the promotion on their respective backs for years, don't just happen...and normally don't happen outside of WrestleMania.

Even two years ago, another Reigns-Cena matchup would have been met with a roll of the eyes by many. But WWE has its finger on the pulse just right with this one—and it's the fans who will benefit the most.