A Broncos season that was filled with head-scratchers concluded with one more.

No, it wasn’t head-scratching that the Broncos fell to the Chiefs in the merciful ending to a forgettable 2017 season. Nor was the fashion in which they lost. These things — losses, poor coaching, imprecise execution and mysterious decision-making — sadly became the norm. A loss to the Chiefs, filled with all of the above, was par for the course.

The mother of all head-scratchers, though, arrived on New Year’s Day. That’s when John Elway tweeted that Vance Joseph would retain his title as head coach of the Denver Broncos, quickly putting an end to any reports to the contrary.

As was asked countless times on talk shows and social media outlets: Why?

There’s little belief that Joseph truly earned another shot as the Broncos head coach. His team’s 5-11 record speaks volumes, but the manner in which he lost — how badly — was unprecedented. The Broncos were embarrassed in 2017, and the head coach did little to stop it. It’s not a stretch to say that the popular opinion in Denver, a sophisticated market when it comes to the NFL, is that Joseph is the worst coach in franchise history. Sure, that’s a matter of opinion, but it was a common one, no doubt.

But back to why?

There are reasons to keep Joseph around.

Money. No matter how fat a cash cow an NFL team may be, no franchise wants to pay a “former” head coach for three seasons.

Personnel. Whether you loved Joseph or hated him, it’s hard to argue that without a legitimate NFL quarterback on the roster he had a major challenge on his hands. Even the best chefs can’t make a great meal with low-grade ingredients. The Broncos had plenty of talent in plenty of places, but quarterback was an undeniable problem.

Lack of viable replacements. It’s one thing to fire the coach. It’s another to replace him. There were a bunch of coaches available following the season; either none of them appealed to Elway (justifiably) or any that did might have said “thanks, but no thanks” sometime prior the calendar flipping.

Continuity. There’s something to be said for not having to start all over. There will be plenty of moving parts at Dove Valley this offseason, perhaps Elway thought adding one more to the mix was something to avoid.

Note: None of those are necessarily good reasons.

It’s easy to spend someone else’s money, but economics dubs this kind of expenditure a sunk cost – what’s done is done, for better or worse. Vegas might call it doubling down on a bad bet. If Joseph doesn’t improve as a head coach, or even if he does but still proves unworthy of guiding one of the best franchises in professional sports, “saving” by not firing him and not hiring his replacement will be a costly choice. The ripple effects of such a horrific season (is there a free agent in the NFL who would willingly want to play for Joseph at or below market value?) could be far-reaching; if the Broncos are bad again, who knows what kind of negative long-term effect keeping Joseph could have.

The team that Joseph took over, by his own admission, was “not broken.” In fact, just one season before, Gary Kubiak coached nearly the same roster — and the same quarterbacks, minus Brock Osweiler, who was arguably the best of the bunch — to a 9-7 record, narrowly missing the playoffs. Kubiak’s offensive line personnel was equally unimpressive. The interior defensive line he coached wasn’t as good as the one Joseph and defensive coordinator Joe Woods commanded. Same roster (maybe better). Same quarterback situation (maybe better with Osweiler). Worse result. What’s the variable?

To be fair, there weren’t many good replacement candidates out there. And the good ones probably had little interest in coming to Denver, given the current status of both the quarterback position and the team’s general state of disarray. But there’s also the argument that anyone — literally anyone (even, say, Denver Post columnist Mark Kiszla) — could be better than Joseph. A change for change’s sake? Why not?

And if consistency is to be valued, then what happened just hours after Elway’s New Year’s Day tweet, was arguably even more head-scratching. Joseph and Elway sent six assistant coaches packing.

Yes, Woods was retained, as was offensive coordinator Bill Musgrave, who assumed the position after Mike McCoy was whacked midseason. But, Jeff Davidson (offensive line), Johnnie Lynn (assistant defensive backs), Brock Olivo (special teams coordinator), Fred Pagac (outside linebackers), Tyke Tolbert (wide recievers) and longstanding Broncos assistant Eric Studesville (assistant head coach and running backs) were all shown the door.

Davidson and Olivo? Sure. Why not. Those two manned two of the NFL’s worst units.

Studesville? It makes no sense. Not only would Studesville’s presence represent the utmost in continuity, but he’s also a pretty darn good coach. Was it his fault that the offense would sway back and forth on its commitment to the run game? Was Studesville to blame for one of the worst offensive lines in football? Should he get some credit for C.J. Anderson’s 1,000-yard season, considering all the obstacles in the way?

Nobody’s claiming that Joseph had a fantastic coaching staff, but if that many of them were bad enough to fire, perhaps a better question might be: Who hired them?

Better yet: Who didn’t he hire? (Anyone remember what Wade Phillips did with this particular defense?)

There are always fall guys, but parting ways with anyone on the list outside of Olivo — who amazingly lasted 16 games — seems like nothing more than semantics. Cutting ties with all of them — including Joseph — would have made more sense. Instead of cutting off the head of the snake, the organization opted to pick off a few scales instead.

But here’s the thing. At this point, any future futility falls on one man and one man only: Elway.

The Duke of Denver could have humbly owned up to a bad hire — a mistake, if you will. He did not. Instead, he doubled down.

If Elway comes up with a competent a signal-caller and Joseph somehow guides the Broncos back to the postseason, well, then ol’ No. 7 still has the ability to escape a collapsing pocket better than just about anyone.

But, next season, if Joseph is what Joseph was, then only Elway is to blame.

Keeping Joseph is a head-scratcher, but there’s nothing mysterious about the line that’s just been drawn in Denver.