DAYTONA BEACH, Fla. — There is one primary reason why the Daytona 500 continues to captivate the imaginations of hardcore NASCAR fans, but also the once-a-year racing passersby. One solitary element keeps Earth’s greatest stock car racers coming back year after year, even when the end result for all but one of them is that they end up hurt, embarrassed, frustrated or all three all at once.

It’s a trick that any good couples counselor will tell you is the key to keeping any relationship exciting, even after 67 years, and even if it’s between human beings and a 2.5-mile superspeedway.

Mystery. Keep them guessing. Right when they think that they have you all figured out, surprise them.

“You didn’t see that coming, did you?!” exclaimed William Byron, standing in Victory Lane on a cool, humid night at the World Center of Racing for the second consecutive year. “I’m being honest, at one point, neither did I.”

It’s cool, Byron. We are all in the same Daytona boat with you. Because everything we thought we knew about this sport’s biggest race, we did not. We never do. And his becoming only the fifth driver to win the 500 back to back is only a small part of a list as long as Sunday’s overtime race took to run.

Tyler Reddick, in a car co-owned by Michael Jordan and the man who was leading late, Denny Hamlin, a team currently suing NASCAR for antitrust, finishing second?

Jimmie Johnson, in his own car, in only one of his two races this year, in a paint scheme designed by Shaquille O’Neal, finishing third?

And Justin Allgaier, driving the first Cup Series car fielded by now-team owner Dale Earnhardt Jr., finishing ninth?

“It’s why we run the races, right?” said a giddy Jeff Gordon, a three-time Daytona 500 winner who made Byron’s No. 24 famous and is now his boss as vice chairman of Hendrick Motorsports.

So, Gordon, you miss wheeling that car into Daytona Victory Lane?

“Absolutely.”

Do you miss the other 500-plus miles of complete and total unpredictable chaos?

“Absolutely not.”

You thought the race was supposed to start at 2:30 p.m. ET? Wrong. The green flag was moved up to 1:30. So, you thought that was when the green was actually going to wave? Wrong again. Because President Donald Trump buzzed overhead in Air Force One, literally stealing the thunder from the U.S. Air Force Thunderbirds, and then led the 41-car field around the speedway with the presidential limo known as “The Beast.”

You thought Chris Evans was Captain America and Tom Cruise was Jack Reacher? Nope. It was grand marshal Anthony Mackie sporting a custom leather Captain American/Great American Race jacket, and it was actor Alan Ritchson, who is roughly twice the size of your average race car driver — including Cole Trickle — who could barely fit his butt-kicking body behind the wheel as honorary pace car driver.

You bought it when they said that “thin band of rain showers coming in from the west” was going to mean a brief yellow flag and small timing hiccup midrace? Nah. It lasted more than four hours. And then there was another. It’s the sixth time in the past 14 years that the 500 has been delayed by rain.

And that was just the non-racing stuff. What happened on the racetrack was even more mind-bending.

See: Cars you thought were gone but were not, but then were gone again. Like Hamlin, a three-time Daytona 500 winner who was in a big early crash, forced to whip his car off the high banks and onto the flat apron, with such force that it sent sparks from his Toyota. Yet, somehow, he was back in the top five with less than 10 laps remaining … only to end up wrecked again as the race ended and he had just been in the lead.

Also, Kyle Busch, still seeking his first Daytona 500 victory after two decades of trying, had an early pit penalty, which stuck him in the back of the pack and got him caught up in a wreck. Then, he too had unbelievably clawed his way into contention late.

Oh, and even though there had been multiple “Big One” crashes during the race’s first 190 laps, with 10 circuits remaining, 29 of the race’s 41 starters were still on the lead lap.

See: The race that spent its first six-and-half decades safely promising it would never become a fuel strategy event, unlike so many of the smaller, sweeping, flat ovals that NASCAR visits throughout the season. Yet, thanks to the still-new Gen 7 race car, even before the race started — and restarted and restarted again — crew chiefs were imploring their drivers to pit for fuel tank top-offs and were all hammering on their miles-per-gallon calculators again with less than 40 laps left.

And see: You thought the Ford Mustangs were unstoppable, right? Of course you did. They were. The Ford drivers were called to their mandatory race morning meeting with Ford Racing brass, including Edsel Ford II, great-grandson of Henry, with their annual message: “Work together. With two laps to go, whatever. But until then, work together.” That working-together worked until it didn’t. Penske Racing Fords — Joey Logano and Ryan Blaney — won the race’s first two stages and led a combined 65 laps, but both were caught up in the same crash with less than 15 laps to go.

Instead, it was Toyota — with 11 cars in the field, spent most of the night beneath an invisibility cloak — that had packed the top 10 when the race restarted with eight laps left. Three ganged up on the lone remaining Penske Ford, Austin Cindric.

Then came the part that we always see coming in the Daytona 500, but with an unforeseen twist. During a big crash with five laps left (the part we know) a 3,400-pound car popped a wheelie and then rolled its way upside down and into the wall (never seen that one before). Ryan Preece, who’d led at the race’s halfway point — in another Ford — walked away from the crash.

And yet, after all of that — all of those wrecks, all of those lap leaders, all of those Toyotas and Fords — there was Byron, whom we hadn’t really heard from since the handful of laps before the rain, and who pilots a Chevy.

“I was so under the radar all week, whenever people talked about favorites, but honestly, that just seems to be how my career has been,” Byron said, grinning, as he was about to pop a champagne cork and spray his team. “Maybe people will figure it out one day.”

Perhaps. But this is the Daytona 500, after all, where we have yet to figure out anything. And also why we keep coming back.